diff --git a/include/hibf/contrib/README.md b/include/hibf/contrib/README.md
new file mode 100644
index 00000000..27373031
--- /dev/null
+++ b/include/hibf/contrib/README.md
@@ -0,0 +1,13 @@
+The `std` directory is a git subtree and includes the content of https://github.com/seqan/seqan-std.
+
+For a general overview regarding `git subtree`, see, for example, https://www.atlassian.com/git/tutorials/git-subtree.
+
+Pulling upstream changes can be achieved by
+```
+git subtree pull --prefix include/hibf/contrib/std https://github.com/seqan/seqan-std.git main --squash
+```
+
+Similarly, you can push subtree changes to your fork:
+```
+git subtree push --prefix include/hibf/contrib/std https://github.com/<user>/seqan-std.git <branch>
+```
diff --git a/include/hibf/contrib/std/chunk_view.hpp b/include/hibf/contrib/std/chunk_view.hpp
index cd3c2487..acff4240 100644
--- a/include/hibf/contrib/std/chunk_view.hpp
+++ b/include/hibf/contrib/std/chunk_view.hpp
@@ -173,7 +173,7 @@ class chunk_view<V>::outer_iterator
         return *x.parent_->current_ == std::ranges::end(x.parent_->base_) && x.parent_->remainder_ != 0;
     }
 
-    friend constexpr difference_type operator-(std::default_sentinel_t y, outer_iterator const & x)
+    friend constexpr difference_type operator-(std::default_sentinel_t, outer_iterator const & x)
         requires std::sized_sentinel_for<std::ranges::sentinel_t<V>, std::ranges::iterator_t<V>>
     {
         auto const dist = std::ranges::end(x.parent_->base_) - *x.parent_->current_;
@@ -270,7 +270,7 @@ class chunk_view<V>::inner_iterator
         return x.parent_->remainder_ == 0;
     }
 
-    friend constexpr difference_type operator-(std::default_sentinel_t y, inner_iterator const & x)
+    friend constexpr difference_type operator-(std::default_sentinel_t, inner_iterator const & x)
         requires std::sized_sentinel_for<std::ranges::sentinel_t<V>, std::ranges::iterator_t<V>>
     {
         std::ranges::min(x.parent_->remainder_, std::ranges::end(x.parent_->base_) - *x.parent_->current_);
@@ -572,7 +572,7 @@ class chunk_view<V>::iterator
         return (x.current_ - y.current_ + x.missing_ - y.missing_) / x.n_;
     }
 
-    friend constexpr difference_type operator-(std::default_sentinel_t y, iterator const & x)
+    friend constexpr difference_type operator-(std::default_sentinel_t, iterator const & x)
         requires std::sized_sentinel_for<std::ranges::sentinel_t<Base>, std::ranges::iterator_t<Base>>
     {
         return seqan::stl::detail::chunk::div_ceil(x.end_ - x.current_, x.n_);
diff --git a/include/hibf/contrib/std/join_with_view.hpp b/include/hibf/contrib/std/join_with_view.hpp
index 0b09c9f1..d83b5b15 100644
--- a/include/hibf/contrib/std/join_with_view.hpp
+++ b/include/hibf/contrib/std/join_with_view.hpp
@@ -88,10 +88,10 @@ class join_with_view :
     Pattern pattern_{};
 
     template <bool Const>
-    struct iterator;
+    class iterator;
 
     template <bool Const>
-    struct sentinel;
+    class sentinel;
 
 public:
     join_with_view()
diff --git a/include/hibf/contrib/std/zip_view.hpp b/include/hibf/contrib/std/zip_view.hpp
index ef168cc2..653014eb 100644
--- a/include/hibf/contrib/std/zip_view.hpp
+++ b/include/hibf/contrib/std/zip_view.hpp
@@ -16,7 +16,8 @@
 
 #include <ranges>
 
-#ifdef __cpp_lib_ranges_zip
+// https://godbolt.org/z/YW7e785sd
+#if defined __cpp_lib_ranges_zip && !defined(__clang__)
 
 namespace seqan::stl::views
 {