diff --git a/include/pybind11/detail/internals.h b/include/pybind11/detail/internals.h
index ad3441576..6d7dc5cfe 100644
--- a/include/pybind11/detail/internals.h
+++ b/include/pybind11/detail/internals.h
@@ -140,6 +140,12 @@ struct type_info {
 /// Tracks the `internals` and `type_info` ABI version independent of the main library version
 #define PYBIND11_INTERNALS_VERSION 3
 
+#if defined(_DEBUG)
+#   define PYBIND11_BUILD_TYPE "_debug"
+#else
+#   define PYBIND11_BUILD_TYPE ""
+#endif
+
 #if defined(WITH_THREAD)
 #  define PYBIND11_INTERNALS_KIND ""
 #else
@@ -147,10 +153,10 @@ struct type_info {
 #endif
 
 #define PYBIND11_INTERNALS_ID "__pybind11_internals_v" \
-    PYBIND11_TOSTRING(PYBIND11_INTERNALS_VERSION) PYBIND11_INTERNALS_KIND "__"
+    PYBIND11_TOSTRING(PYBIND11_INTERNALS_VERSION) PYBIND11_INTERNALS_KIND PYBIND11_BUILD_TYPE "__"
 
 #define PYBIND11_MODULE_LOCAL_ID "__pybind11_module_local_v" \
-    PYBIND11_TOSTRING(PYBIND11_INTERNALS_VERSION) PYBIND11_INTERNALS_KIND "__"
+    PYBIND11_TOSTRING(PYBIND11_INTERNALS_VERSION) PYBIND11_INTERNALS_KIND PYBIND11_BUILD_TYPE "__"
 
 /// Each module locally stores a pointer to the `internals` data. The data
 /// itself is shared among modules with the same `PYBIND11_INTERNALS_ID`.