diff --git a/python/templates/CollectionData.cc.jinja2 b/python/templates/CollectionData.cc.jinja2
index 6561d744a..a84710d16 100644
--- a/python/templates/CollectionData.cc.jinja2
+++ b/python/templates/CollectionData.cc.jinja2
@@ -38,6 +38,21 @@
   if (!isSubsetColl) {
     m_data.reset(buffers.dataAsVector<{{ class.full_type }}Data>());
 
+  // The following is ugly code for the case when reading garbage data from ROOT
+  // after calling dataAsVector, which can trigger infinite loops that consume
+  // all the available memory and this works at least for GCC 15 and Clang 20 in
+  // {Debug,RelWithDebInfo,Release} modes.
+  // https://github.com/AIDASoft/podio/pull/817#issuecomment-3266748609 and
+  // https://github.com/AIDASoft/podio/pull/842
+  volatile std::uint64_t s = m_data->size();
+  if (s > 1e15) throw std::runtime_error("Bad data after reading: a collection is too big");
+  else
+    if (s == 0)
+      for ([[maybe_unused]] const auto& _ : *m_data.get())
+        throw std::runtime_error("Bad data after reading: zero-sized collection with data");
+  // end of ugly
+
+
 {% for member in VectorMembers %}
   m_vec_{{ member.name }}.reset(podio::CollectionReadBuffers::asVector<{{ member.full_type }}>(m_vecmem_info[{{ loop.index0 }}].second));
 {% endfor %}