diff --git a/lib/area.cc b/lib/area.cc
index 6b4fb75c..3f75cc64 100644
--- a/lib/area.cc
+++ b/lib/area.cc
@@ -21,7 +21,7 @@ namespace {
 
 using MpManager = osmium::area::MultipolygonManager<osmium::area::Assembler>;
 
-class AreaManagerSecondPassHandlerBase : public BaseHandler
+class AreaManagerSecondPassHandlerBase : public pyosmium::BaseHandler
 {
 public:
     AreaManagerSecondPassHandlerBase(MpManager *mp_manager)
@@ -69,7 +69,7 @@ class AreaManagerSecondPassHandler : public AreaManagerSecondPassHandlerBase
 
 private:
     py::args m_args;
-    HandlerChain m_handlers;
+    pyosmium::HandlerChain m_handlers;
 
 };
 
@@ -86,14 +86,14 @@ class AreaManagerBufferHandler : public AreaManagerSecondPassHandlerBase
 };
 
 
-class AreaManager : public BaseHandler
+class AreaManager : public pyosmium::BaseHandler
 {
 public:
     AreaManager()
     : m_mp_manager(m_assembler_config)
     {}
 
-    BaseHandler *first_pass_handler() { return this; }
+    pyosmium::BaseHandler *first_pass_handler() { return this; }
 
     // first-pass-handler
     bool relation(osmium::Relation const *r) override
@@ -119,16 +119,16 @@ class AreaManager : public BaseHandler
     osmium::area::MultipolygonManager<osmium::area::Assembler> m_mp_manager;
 };
 
-}
+} // namespace
 
 PYBIND11_MODULE(_area, m)
 {
-    py::class_<AreaManagerSecondPassHandler, BaseHandler>(m,
+    py::class_<AreaManagerSecondPassHandler, pyosmium::BaseHandler>(m,
                 "AreaManagerSecondPassHandler");
-    py::class_<AreaManagerBufferHandler, BaseHandler>(m,
+    py::class_<AreaManagerBufferHandler, pyosmium::BaseHandler>(m,
                 "AreaManagerBufferHandler");
 
-    py::class_<AreaManager, BaseHandler>(m, "AreaManager",
+    py::class_<AreaManager, pyosmium::BaseHandler>(m, "AreaManager",
         "Object manager class that manages building area objects from "
         "ways and relations.")
         .def(py::init<>())
diff --git a/lib/base_handler.h b/lib/base_handler.h
index 11359af3..18b9e8d5 100644
--- a/lib/base_handler.h
+++ b/lib/base_handler.h
@@ -10,6 +10,8 @@
 
 #include <osmium/handler.hpp>
 
+namespace pyosmium {
+
 class BaseHandler : public osmium::handler::Handler
 {
 public:
@@ -36,4 +38,6 @@ class BaseHandler : public osmium::handler::Handler
     virtual void flush() {}
 };
 
+} // namespace
+
 #endif // PYOSMIUM_BASE_HANDLER_HPP
diff --git a/lib/cast.h b/lib/cast.h
index a56121e7..4ff547ff 100644
--- a/lib/cast.h
+++ b/lib/cast.h
@@ -2,7 +2,7 @@
  *
  * This file is part of pyosmium. (https://osmcode.org/pyosmium/)
  *
- * Copyright (C) 2023 Sarah Hoffmann <lonvia@denofr.de> and others.
+ * Copyright (C) 2024 Sarah Hoffmann <lonvia@denofr.de> and others.
  * For a full list of authors see the git log.
  */
 #ifndef PYOSMIUM_CAST_H
@@ -122,6 +122,6 @@ T const &cast_list(pybind11::object const &o) {
     return o.attr("_list").cast<T const &>();
 }
 
-}
+} // namespace
 
 #endif // PYOSMIUM_CAST_H
diff --git a/lib/empty_tag_filter.cc b/lib/empty_tag_filter.cc
index f1bc556b..fcf0b023 100644
--- a/lib/empty_tag_filter.cc
+++ b/lib/empty_tag_filter.cc
@@ -29,7 +29,7 @@ class EmptyTagFilter : public pyosmium::BaseFilter
 
 };
 
-}
+} // namespace
 
 namespace pyosmium {
 
diff --git a/lib/file_iterator.cc b/lib/file_iterator.cc
index 7f0fc528..1923e612 100644
--- a/lib/file_iterator.cc
+++ b/lib/file_iterator.cc
@@ -63,7 +63,7 @@ class OsmFileIterator
                 {
                     auto *node = static_cast<osmium::Node *>(entity);
                     if (!m_pre_handler.handle_node(*node)) {
-                        m_current = m_type_module.attr("Node")(COSMNode{node});
+                        m_current = m_type_module.attr("Node")(pyosmium::COSMNode{node});
                         m_current_type = osmium::item_type::node;
                         return m_current;
                     }
@@ -73,7 +73,7 @@ class OsmFileIterator
                 {
                     auto *way = static_cast<osmium::Way *>(entity);
                     if (!m_pre_handler.handle_way(*way)) {
-                        m_current = m_type_module.attr("Way")(COSMWay{way});
+                        m_current = m_type_module.attr("Way")(pyosmium::COSMWay{way});
                         m_current_type = osmium::item_type::way;
                         return m_current;
                     }
@@ -83,7 +83,7 @@ class OsmFileIterator
                 {
                     auto *rel = static_cast<osmium::Relation *>(entity);
                     if (!m_pre_handler.handle_relation(*rel)) {
-                        m_current = m_type_module.attr("Relation")(COSMRelation{rel});
+                        m_current = m_type_module.attr("Relation")(pyosmium::COSMRelation{rel});
                         m_current_type = osmium::item_type::relation;
                         return m_current;
                     }
@@ -93,7 +93,7 @@ class OsmFileIterator
                 {
                     auto *cs = static_cast<osmium::Changeset *>(entity);
                     if (!m_pre_handler.handle_changeset(*cs)) {
-                        m_current = m_type_module.attr("Changeset")(COSMChangeset{cs});
+                        m_current = m_type_module.attr("Changeset")(pyosmium::COSMChangeset{cs});
                         m_current_type = osmium::item_type::changeset;
                         return m_current;
                     }
@@ -112,16 +112,16 @@ class OsmFileIterator
     {
         switch (m_current_type) {
             case osmium::item_type::node:
-                m_current.attr("_pyosmium_data").template cast<COSMNode *>()->invalidate();
+                m_current.attr("_pyosmium_data").template cast<pyosmium::COSMNode *>()->invalidate();
                 break;
             case osmium::item_type::way:
-                m_current.attr("_pyosmium_data").template cast<COSMWay *>()->invalidate();
+                m_current.attr("_pyosmium_data").template cast<pyosmium::COSMWay *>()->invalidate();
                 break;
             case osmium::item_type::relation:
-                m_current.attr("_pyosmium_data").template cast<COSMRelation *>()->invalidate();
+                m_current.attr("_pyosmium_data").template cast<pyosmium::COSMRelation *>()->invalidate();
                 break;
             case osmium::item_type::changeset:
-                m_current.attr("_pyosmium_data").template cast<COSMChangeset *>()->invalidate();
+                m_current.attr("_pyosmium_data").template cast<pyosmium::COSMChangeset *>()->invalidate();
                 break;
         }
         m_current_type = osmium::item_type::undefined;
@@ -133,12 +133,14 @@ class OsmFileIterator
     osmium::item_type m_current_type = osmium::item_type::undefined;
     pybind11::object m_current;
 
-    HandlerChain m_pre_handler;
+    pyosmium::HandlerChain m_pre_handler;
 
     pybind11::object m_type_module = pybind11::module_::import("osmium.osm.types");
 };
 
-}
+} // namespace
+
+namespace pyosmium {
 
 void init_osm_file_iterator(py::module &m)
 {
@@ -151,3 +153,4 @@ void init_osm_file_iterator(py::module &m)
         ;
 }
 
+} // namespace
diff --git a/lib/filter.cc b/lib/filter.cc
index 92d819e9..e3a9fec0 100644
--- a/lib/filter.cc
+++ b/lib/filter.cc
@@ -13,7 +13,7 @@
 namespace py = pybind11;
 
 PYBIND11_MODULE(_filter, m) {
-    py::class_<pyosmium::BaseFilter, BaseHandler>(m, "BaseFilter")
+    py::class_<pyosmium::BaseFilter, pyosmium::BaseHandler>(m, "BaseFilter")
         .def("enable_for", &pyosmium::BaseFilter::enable_for,
              py::arg("entities"),
              "Set the OSM types this filter should be used for.")
diff --git a/lib/geom.cc b/lib/geom.cc
index b637f0aa..46670270 100644
--- a/lib/geom.cc
+++ b/lib/geom.cc
@@ -2,7 +2,7 @@
  *
  * This file is part of pyosmium. (https://osmcode.org/pyosmium/)
  *
- * Copyright (C) 2023 Sarah Hoffmann <lonvia@denofr.de> and others.
+ * Copyright (C) 2024 Sarah Hoffmann <lonvia@denofr.de> and others.
  * For a full list of authors see the git log.
  */
 #include <pybind11/pybind11.h>
@@ -21,6 +21,8 @@
 namespace py = pybind11;
 namespace og = osmium::geom;
 
+namespace {
+
 struct WKBFactory : osmium::geom::WKBFactory<>
 {
 public:
@@ -46,7 +48,7 @@ void make_factory_class(py::module_ &m, char const *name, char const *doc)
                  if (py::isinstance<osmium::Location>(o)) {
                     return f.create_point(o.cast<osmium::Location const &>());
                  }
-                 auto const *node = pyosmium::try_cast<COSMNode>(o);
+                 auto const *node = pyosmium::try_cast<pyosmium::COSMNode>(o);
                  if (node) {
                     return f.create_point(*node->get());
                  }
@@ -57,7 +59,7 @@ void make_factory_class(py::module_ &m, char const *name, char const *doc)
              "Create a point geometry from a :py:class:`osmium.osm.Node`.")
         .def("create_linestring",
              [](Factory &f, py::object const &o, og::use_nodes un, og::direction dir) {
-                 auto const *way = pyosmium::try_cast<COSMWay>(o);
+                 auto const *way = pyosmium::try_cast<pyosmium::COSMWay>(o);
                  if (way) {
                     return f.create_linestring(*way->get(), un, dir);
                  }
@@ -69,13 +71,15 @@ void make_factory_class(py::module_ &m, char const *name, char const *doc)
              "Create a LineString geometry from a :py:class:`osmium.osm.Way`.")
         .def("create_multipolygon",
              [](Factory &f, py::object const &o) {
-                 return f.create_multipolygon(*pyosmium::cast<COSMArea>(o).get());
+                 return f.create_multipolygon(*pyosmium::cast<pyosmium::COSMArea>(o).get());
              },
              py::arg("area"),
              "Create a MultiPolygon geometry from a :py:class:`osmium.osm.Area`.")
     ;
 }
 
+} // namespace
+
 PYBIND11_MODULE(geom, m)
 {
     py::enum_<og::use_nodes>(m, "use_nodes")
diff --git a/lib/handler_chain.h b/lib/handler_chain.h
index dad49ca2..e8fd455c 100644
--- a/lib/handler_chain.h
+++ b/lib/handler_chain.h
@@ -19,6 +19,8 @@
 
 namespace py = pybind11;
 
+namespace pyosmium {
+
 class HandlerChain : public osmium::handler::Handler
 {
 public:
@@ -109,4 +111,6 @@ class HandlerChain : public osmium::handler::Handler
     std::vector<pyosmium::PythonHandler> m_python_handlers;
 };
 
+} // namespace
+
 #endif //PYOSMIUM_HANDLER_CHAIN_H
diff --git a/lib/io.cc b/lib/io.cc
index 5cbb7cb3..b8a48c3a 100644
--- a/lib/io.cc
+++ b/lib/io.cc
@@ -2,7 +2,7 @@
  *
  * This file is part of pyosmium. (https://osmcode.org/pyosmium/)
  *
- * Copyright (C) 2023 Sarah Hoffmann <lonvia@denofr.de> and others.
+ * Copyright (C) 2024 Sarah Hoffmann <lonvia@denofr.de> and others.
  * For a full list of authors see the git log.
  */
 #include <pybind11/pybind11.h>
@@ -19,7 +19,7 @@ class FileBuffer : public osmium::io::File
     using osmium::io::File::File;
 };
 
-}
+} // namespace
 
 
 PYBIND11_MODULE(io, m)
diff --git a/lib/key_filter.cc b/lib/key_filter.cc
index d65819a2..28ff394b 100644
--- a/lib/key_filter.cc
+++ b/lib/key_filter.cc
@@ -62,7 +62,7 @@ class KeyFilter : public pyosmium::BaseFilter
     std::vector<std::string> m_keys;
 };
 
-}
+} // namespace
 
 namespace pyosmium {
 
diff --git a/lib/merge_input_reader.cc b/lib/merge_input_reader.cc
index 1c4671fd..ad0902fb 100644
--- a/lib/merge_input_reader.cc
+++ b/lib/merge_input_reader.cc
@@ -62,7 +62,7 @@ class MergeInputReader
 public:
     void apply(py::args args, std::string const &idx, bool simplify)
     {
-        HandlerChain handler{args};
+        pyosmium::HandlerChain handler{args};
         if (idx.empty())
             apply_without_location(handler, simplify);
         else
@@ -128,7 +128,7 @@ class MergeInputReader
     }
 
 private:
-    void apply_without_location(HandlerChain& handler, bool simplify)
+    void apply_without_location(pyosmium::HandlerChain& handler, bool simplify)
     {
         if (simplify) {
             objects.sort(osmium::object_order_type_id_reverse_version());
@@ -150,7 +150,7 @@ class MergeInputReader
         changes.clear();
     }
 
-    void apply_with_location(HandlerChain& handler, std::string const &idx,
+    void apply_with_location(pyosmium::HandlerChain& handler, std::string const &idx,
                              bool simplify)
     {
         using Index_fab =
@@ -199,7 +199,9 @@ class MergeInputReader
     osmium::ObjectPointerCollection objects;
 };
 
-}
+} // namespace
+
+namespace pyosmium {
 
 void init_merge_input_reader(py::module &m)
 {
@@ -240,3 +242,5 @@ void init_merge_input_reader(py::module &m)
              "safely discarded after the function has been called.")
     ;
 };
+
+} // namespace
diff --git a/lib/node_location_handler.cc b/lib/node_location_handler.cc
index e164e3c8..61c56411 100644
--- a/lib/node_location_handler.cc
+++ b/lib/node_location_handler.cc
@@ -12,13 +12,14 @@
 
 #include "base_handler.h"
 
+namespace {
+
 using LocationTable =
         osmium::index::map::Map<osmium::unsigned_object_id_type, osmium::Location>;
 using NodeLocationHandler =
         osmium::handler::NodeLocationsForWays<LocationTable>;
 
-
-class NodeLocationsForWays : public BaseHandler
+class NodeLocationsForWays : public pyosmium::BaseHandler
 {
 public:
     NodeLocationsForWays(LocationTable &idx)
@@ -50,8 +51,12 @@ class NodeLocationsForWays : public BaseHandler
     bool apply_nodes_to_ways = true;
 };
 
+} // namespace
+
 namespace py = pybind11;
 
+namespace pyosmium {
+
 void init_node_location_handler(py::module &m)
 {
     py::class_<NodeLocationsForWays, BaseHandler>(m, "NodeLocationsForWays")
@@ -65,3 +70,5 @@ void init_node_location_handler(py::module &m)
     ;
 
 }
+
+} // namespace
diff --git a/lib/osm.cc b/lib/osm.cc
index 3db1f7e9..03e42183 100644
--- a/lib/osm.cc
+++ b/lib/osm.cc
@@ -2,7 +2,7 @@
  *
  * This file is part of pyosmium. (https://osmcode.org/pyosmium/)
  *
- * Copyright (C) 2023 Sarah Hoffmann <lonvia@denofr.de> and others.
+ * Copyright (C) 2024 Sarah Hoffmann <lonvia@denofr.de> and others.
  * For a full list of authors see the git log.
  */
 #include <pybind11/pybind11.h>
@@ -15,9 +15,6 @@
 
 namespace py = pybind11;
 
-using TagIterator = osmium::TagList::const_iterator;
-using MemberIterator = osmium::RelationMemberList::const_iterator;
-
 #if PYBIND11_VERSION_MINOR >= 11 || PYBIND11_VERSION_MAJOR > 2
 /*
 Work-around false positive added by pybind/pybind11@f701654 change:
@@ -50,6 +47,11 @@ struct is_move_constructible<osmium::memory::ItemIterator<T>>
 } // namespace pybind11
 #endif
 
+namespace {
+
+using TagIterator = osmium::TagList::const_iterator;
+using MemberIterator = osmium::RelationMemberList::const_iterator;
+
 static py::object tag_iterator_next(TagIterator &it, TagIterator const &cend)
 {
     if (it == cend)
@@ -147,6 +149,8 @@ py::class_<COSMObject> make_osm_object_class(py::module_ &m, char const *class_n
     ;
 }
 
+} // namespace
+
 
 PYBIND11_MODULE(_osm, m) {
     py::enum_<osmium::osm_entity_bits::type>(m, "osm_entity_bits")
@@ -246,68 +250,68 @@ PYBIND11_MODULE(_osm, m) {
     py::class_<InnerRingIterator>(m, "CInnerRingIterator");
 
 
-    make_osm_object_class<COSMNode>(m, "COSMNode")
-        .def("location", [](COSMNode const &o) { return o.get()->location(); })
+    make_osm_object_class<pyosmium::COSMNode>(m, "COSMNode")
+        .def("location", [](pyosmium::COSMNode const &o) { return o.get()->location(); })
     ;
 
-    make_osm_object_class<COSMWay>(m, "COSMWay")
-        .def("is_closed", [](COSMWay const &o) { return o.get()->is_closed(); })
-        .def("ends_have_same_location", [](COSMWay const &o) { return o.get()->ends_have_same_location(); })
-        .def("nodes", [](COSMWay const &o) { return &o.get()->nodes(); },
+    make_osm_object_class<pyosmium::COSMWay>(m, "COSMWay")
+        .def("is_closed", [](pyosmium::COSMWay const &o) { return o.get()->is_closed(); })
+        .def("ends_have_same_location", [](pyosmium::COSMWay const &o) { return o.get()->ends_have_same_location(); })
+        .def("nodes", [](pyosmium::COSMWay const &o) { return &o.get()->nodes(); },
              py::return_value_policy::reference)
     ;
 
 
-    make_osm_object_class<COSMRelation>(m, "COSMRelation")
-        .def("members_size", [](COSMRelation const &o) { return o.get()->members().size(); })
-        .def("members_begin", [](COSMRelation const &o) { return o.get()->members().cbegin(); })
-        .def("members_next", [](COSMRelation const &o, MemberIterator &it)
+    make_osm_object_class<pyosmium::COSMRelation>(m, "COSMRelation")
+        .def("members_size", [](pyosmium::COSMRelation const &o) { return o.get()->members().size(); })
+        .def("members_begin", [](pyosmium::COSMRelation const &o) { return o.get()->members().cbegin(); })
+        .def("members_next", [](pyosmium::COSMRelation const &o, MemberIterator &it)
             { return member_iterator_next(it, o.get()->members().cend()); })
 
     ;
 
-    make_osm_object_class<COSMArea>(m, "COSMArea")
-        .def("from_way", [](COSMArea const &o) { return o.get()->from_way(); })
-        .def("orig_id", [](COSMArea const &o) { return o.get()->orig_id(); })
-        .def("is_multipolygon", [](COSMArea const &o) { return o.get()->is_multipolygon(); })
-        .def("num_rings", [](COSMArea const &o) { return o.get()->num_rings(); })
-        .def("outer_begin", [](COSMArea const &o) { return o.get()->outer_rings().cbegin(); })
-        .def("outer_next", [](COSMArea const &o, OuterRingIterator &it) {
+    make_osm_object_class<pyosmium::COSMArea>(m, "COSMArea")
+        .def("from_way", [](pyosmium::COSMArea const &o) { return o.get()->from_way(); })
+        .def("orig_id", [](pyosmium::COSMArea const &o) { return o.get()->orig_id(); })
+        .def("is_multipolygon", [](pyosmium::COSMArea const &o) { return o.get()->is_multipolygon(); })
+        .def("num_rings", [](pyosmium::COSMArea const &o) { return o.get()->num_rings(); })
+        .def("outer_begin", [](pyosmium::COSMArea const &o) { return o.get()->outer_rings().cbegin(); })
+        .def("outer_next", [](pyosmium::COSMArea const &o, OuterRingIterator &it) {
             o.get();
             return ring_iterator_next<osmium::OuterRing>(it);
         },
              py::return_value_policy::reference)
-        .def("inner_begin", [](COSMArea const &o, osmium::OuterRing const &ring)
+        .def("inner_begin", [](pyosmium::COSMArea const &o, osmium::OuterRing const &ring)
             { return o.get()->inner_rings(ring).cbegin(); })
-        .def("inner_next", [](COSMArea const &o, InnerRingIterator &it) {
+        .def("inner_next", [](pyosmium::COSMArea const &o, InnerRingIterator &it) {
             o.get();
             return ring_iterator_next<osmium::InnerRing>(it);
         },
              py::return_value_policy::reference)
     ;
 
-    py::class_<COSMChangeset>(m, "COSMChangeset")
-        .def("id", [](COSMChangeset const &o) { return o.get()->id(); })
-        .def("uid", [](COSMChangeset const &o) { return o.get()->uid(); })
-        .def("created_at", [](COSMChangeset const &o) { return o.get()->created_at(); })
-        .def("closed_at", [](COSMChangeset const &o) { return o.get()->closed_at(); })
-        .def("open", [](COSMChangeset const &o) { return o.get()->open(); })
-        .def("num_changes", [](COSMChangeset const &o) { return o.get()->num_changes(); })
-        .def("user", [](COSMChangeset const &o) { return o.get()->user(); })
-        .def("user_is_anonymous", [](COSMChangeset const &o) { return o.get()->user_is_anonymous(); })
-        .def("bounds", [](COSMChangeset const &o) { return o.get()->bounds(); })
-        .def("tags_size", [](COSMChangeset const &o) { return o.get()->tags().size(); })
-        .def("tags_get_value_by_key", [](COSMChangeset const &o, char const *key, char const *def)
+    py::class_<pyosmium::COSMChangeset>(m, "COSMChangeset")
+        .def("id", [](pyosmium::COSMChangeset const &o) { return o.get()->id(); })
+        .def("uid", [](pyosmium::COSMChangeset const &o) { return o.get()->uid(); })
+        .def("created_at", [](pyosmium::COSMChangeset const &o) { return o.get()->created_at(); })
+        .def("closed_at", [](pyosmium::COSMChangeset const &o) { return o.get()->closed_at(); })
+        .def("open", [](pyosmium::COSMChangeset const &o) { return o.get()->open(); })
+        .def("num_changes", [](pyosmium::COSMChangeset const &o) { return o.get()->num_changes(); })
+        .def("user", [](pyosmium::COSMChangeset const &o) { return o.get()->user(); })
+        .def("user_is_anonymous", [](pyosmium::COSMChangeset const &o) { return o.get()->user_is_anonymous(); })
+        .def("bounds", [](pyosmium::COSMChangeset const &o) { return o.get()->bounds(); })
+        .def("tags_size", [](pyosmium::COSMChangeset const &o) { return o.get()->tags().size(); })
+        .def("tags_get_value_by_key", [](pyosmium::COSMChangeset const &o, char const *key, char const *def)
             { return o.get()->tags().get_value_by_key(key, def); })
-        .def("tags_has_key", [](COSMChangeset const &o, char const *key)
+        .def("tags_has_key", [](pyosmium::COSMChangeset const &o, char const *key)
             { return o.get()->tags().has_key(key); })
-        .def("tags_begin", [](COSMChangeset const &o) { return o.get()->tags().cbegin(); })
-        .def("tags_next", [](COSMChangeset const &o, TagIterator &it)
+        .def("tags_begin", [](pyosmium::COSMChangeset const &o) { return o.get()->tags().cbegin(); })
+        .def("tags_next", [](pyosmium::COSMChangeset const &o, TagIterator &it)
             { return tag_iterator_next(it, o.get()->tags().cend()); })
-        .def("is_valid", &COSMChangeset::is_valid)
+        .def("is_valid", &pyosmium::COSMChangeset::is_valid)
     ;
 
-    make_node_list<osmium::WayNodeList, COSMWay>(m, "CWayNodeList");
-    make_node_list<osmium::OuterRing, COSMArea>(m, "COuterRing");
-    make_node_list<osmium::InnerRing, COSMArea>(m, "CInnerRing");
+    make_node_list<osmium::WayNodeList, pyosmium::COSMWay>(m, "CWayNodeList");
+    make_node_list<osmium::OuterRing, pyosmium::COSMArea>(m, "COuterRing");
+    make_node_list<osmium::InnerRing, pyosmium::COSMArea>(m, "CInnerRing");
 }
diff --git a/lib/osm_base_objects.h b/lib/osm_base_objects.h
index bb48e39a..c1745c76 100644
--- a/lib/osm_base_objects.h
+++ b/lib/osm_base_objects.h
@@ -2,7 +2,7 @@
  *
  * This file is part of pyosmium. (https://osmcode.org/pyosmium/)
  *
- * Copyright (C) 2023 Sarah Hoffmann <lonvia@denofr.de> and others.
+ * Copyright (C) 2024 Sarah Hoffmann <lonvia@denofr.de> and others.
  * For a full list of authors see the git log.
  */
 #ifndef PYOSMIUM_OSM_BASE_OBJECTS_HPP
@@ -12,6 +12,8 @@
 
 #include <osmium/osm.hpp>
 
+namespace pyosmium {
+
 template <typename T>
 class COSMDerivedObject {
 public:
@@ -38,5 +40,6 @@ using COSMRelation = COSMDerivedObject<osmium::Relation const>;
 using COSMArea = COSMDerivedObject<osmium::Area const>;
 using COSMChangeset = COSMDerivedObject<osmium::Changeset const>;
 
+} // namespace
 
 #endif //PYOSMIUM_OSM_BASE_OBJECTS_HPP
diff --git a/lib/osmium.cc b/lib/osmium.cc
index 89e77148..499c7c4b 100644
--- a/lib/osmium.cc
+++ b/lib/osmium.cc
@@ -32,13 +32,13 @@ PYBIND11_MODULE(_osmium, m) {
         }
     });
 
-    m.def("apply", [](osmium::io::Reader &rd, BaseHandler &h)
+    m.def("apply", [](osmium::io::Reader &rd, pyosmium::BaseHandler &h)
                    { py::gil_scoped_release release; osmium::apply(rd, h); },
           py::arg("reader"), py::arg("handler"),
           "Apply a single handler.");
     m.def("apply", [](osmium::io::Reader &rd, py::args args)
                      {
-                         HandlerChain handler{args};
+                         pyosmium::HandlerChain handler{args};
                          {
                              py::gil_scoped_release release;
                              osmium::apply(rd, handler);
@@ -46,7 +46,7 @@ PYBIND11_MODULE(_osmium, m) {
                      },
           py::arg("reader"),
           "Apply a chain of handlers.");
-    m.def("apply", [](std::string fn, BaseHandler &h)
+    m.def("apply", [](std::string fn, pyosmium::BaseHandler &h)
                    {
                        py::gil_scoped_release release;
                        osmium::io::Reader rd{fn};
@@ -56,7 +56,7 @@ PYBIND11_MODULE(_osmium, m) {
           "Apply a single handler.");
     m.def("apply", [](std::string fn, py::args args)
                      {
-                         HandlerChain handler{args};
+                         pyosmium::HandlerChain handler{args};
                          {
                              py::gil_scoped_release release;
                              osmium::io::Reader rd{fn};
@@ -66,7 +66,7 @@ PYBIND11_MODULE(_osmium, m) {
           py::arg("filename"),
           "Apply a chain of handlers.");
 
-    py::class_<BaseHandler>(m, "BaseHandler");
+    py::class_<pyosmium::BaseHandler>(m, "BaseHandler");
 
     py::class_<pyosmium::BufferIterator>(m, "BufferIterator",
     "Iterator interface for reading from a queue of buffers.")
@@ -77,9 +77,9 @@ PYBIND11_MODULE(_osmium, m) {
          "Get the next OSM object from the buffer or raise an StopIteration.")
     ;
 
-    init_merge_input_reader(m);
-    init_write_handler(m);
-    init_simple_writer(m);
-    init_node_location_handler(m);
-    init_osm_file_iterator(m);
+    pyosmium::init_merge_input_reader(m);
+    pyosmium::init_write_handler(m);
+    pyosmium::init_simple_writer(m);
+    pyosmium::init_node_location_handler(m);
+    pyosmium::init_osm_file_iterator(m);
 };
diff --git a/lib/osmium_module.h b/lib/osmium_module.h
index ac425591..9bf1aba6 100644
--- a/lib/osmium_module.h
+++ b/lib/osmium_module.h
@@ -10,10 +10,14 @@
 
 #include <pybind11/pybind11.h>
 
+namespace pyosmium {
+
 void init_merge_input_reader(pybind11::module &m);
 void init_write_handler(pybind11::module &m);
 void init_simple_writer(pybind11::module &m);
 void init_node_location_handler(pybind11::module &m);
 void init_osm_file_iterator(pybind11::module &m);
 
+} // namespace
+
 #endif // PYOSMIUM_OSMIUM_MODULE_H
diff --git a/lib/replication.cc b/lib/replication.cc
index 66520719..88a02320 100644
--- a/lib/replication.cc
+++ b/lib/replication.cc
@@ -2,7 +2,7 @@
  *
  * This file is part of pyosmium. (https://osmcode.org/pyosmium/)
  *
- * Copyright (C) 2023 Sarah Hoffmann <lonvia@denofr.de> and others.
+ * Copyright (C) 2024 Sarah Hoffmann <lonvia@denofr.de> and others.
  * For a full list of authors see the git log.
  */
 #include <pybind11/pybind11.h>
@@ -15,6 +15,8 @@
 
 namespace py = pybind11;
 
+namespace {
+
 struct LastChangeHandler : public osmium::handler::Handler
 {
     osmium::Timestamp last_change;
@@ -27,6 +29,7 @@ struct LastChangeHandler : public osmium::handler::Handler
     }
 };
 
+} // namespace
 
 PYBIND11_MODULE(_replication, m)
 {
diff --git a/lib/simple_writer.cc b/lib/simple_writer.cc
index fab7eeab..1a355028 100644
--- a/lib/simple_writer.cc
+++ b/lib/simple_writer.cc
@@ -2,7 +2,7 @@
  *
  * This file is part of pyosmium. (https://osmcode.org/pyosmium/)
  *
- * Copyright (C) 2023 Sarah Hoffmann <lonvia@denofr.de> and others.
+ * Copyright (C) 2024 Sarah Hoffmann <lonvia@denofr.de> and others.
  * For a full list of authors see the git log.
  */
 #include <pybind11/pybind11.h>
@@ -44,7 +44,7 @@ class SimpleWriter
 
         buffer.rollback();
 
-        auto const *inode = pyosmium::try_cast<COSMNode>(o);
+        auto const *inode = pyosmium::try_cast<pyosmium::COSMNode>(o);
         if (inode) {
             buffer.add_item(*inode->get());
         } else {
@@ -57,7 +57,7 @@ class SimpleWriter
             }
 
             set_common_attributes(o, builder);
-            set_taglist<COSMNode>(o, builder);
+            set_taglist<pyosmium::COSMNode>(o, builder);
         }
 
         flush_buffer();
@@ -71,7 +71,7 @@ class SimpleWriter
 
         buffer.rollback();
 
-        auto const *iobj = pyosmium::try_cast<COSMWay>(o);
+        auto const *iobj = pyosmium::try_cast<pyosmium::COSMWay>(o);
         if (iobj) {
             buffer.add_item(*iobj->get());
         } else {
@@ -79,7 +79,7 @@ class SimpleWriter
 
             set_common_attributes(o, builder);
             set_nodelist(o, &builder);
-            set_taglist<COSMWay>(o, builder);
+            set_taglist<pyosmium::COSMWay>(o, builder);
         }
 
         flush_buffer();
@@ -93,7 +93,7 @@ class SimpleWriter
 
         buffer.rollback();
 
-        auto const *iobj = pyosmium::try_cast<COSMRelation>(o);
+        auto const *iobj = pyosmium::try_cast<pyosmium::COSMRelation>(o);
         if (iobj) {
             buffer.add_item(*iobj->get());
         } else {
@@ -101,7 +101,7 @@ class SimpleWriter
 
             set_common_attributes(o, builder);
             set_memberlist(o, &builder);
-            set_taglist<COSMRelation>(o, builder);
+            set_taglist<pyosmium::COSMRelation>(o, builder);
         }
 
         flush_buffer();
@@ -242,7 +242,7 @@ class SimpleWriter
         }
 
         // original memberlist
-        auto const &iobj = pyosmium::try_cast<COSMRelation>(o);
+        auto const &iobj = pyosmium::try_cast<pyosmium::COSMRelation>(o);
         if (iobj) {
             auto const &oml = iobj->get()->members();
             if (oml.size() > 0)
@@ -300,7 +300,9 @@ class SimpleWriter
     size_t buffer_size;
 };
 
-}
+} // namespace
+
+namespace pyosmium {
 
 void init_simple_writer(pybind11::module &m)
 {
@@ -335,3 +337,5 @@ void init_simple_writer(pybind11::module &m)
              "that the buffer memory can be freed.")
     ;
 }
+
+} // namespace
diff --git a/lib/write_handler.cc b/lib/write_handler.cc
index 427b4e95..a05b1a5d 100644
--- a/lib/write_handler.cc
+++ b/lib/write_handler.cc
@@ -15,7 +15,7 @@
 
 namespace {
 
-class WriteHandler : public BaseHandler
+class WriteHandler : public pyosmium::BaseHandler
 {
     enum { BUFFER_WRAP = 4096 };
 
@@ -88,10 +88,12 @@ class WriteHandler : public BaseHandler
     osmium::memory::Buffer buffer;
 };
 
-}
+} // namespace
 
 namespace py = pybind11;
 
+namespace pyosmium {
+
 void init_write_handler(pybind11::module &m)
 {
     py::class_<WriteHandler, BaseHandler>(m, "WriteHandler",
@@ -117,3 +119,5 @@ void init_write_handler(pybind11::module &m)
              "that the buffer memory can be freed.")
     ;
 }
+
+} // namespace