diff --git a/include/pybind11/cast.h b/include/pybind11/cast.h
index 4c3abc1c7..537b217ef 100644
--- a/include/pybind11/cast.h
+++ b/include/pybind11/cast.h
@@ -603,7 +603,7 @@ public:
     /// Try to load with foreign typeinfo, if available. Used when there is no
     /// native typeinfo, or when the native one wasn't able to produce a value.
     PYBIND11_NOINLINE bool try_load_foreign_module_local(handle src) {
-        constexpr auto *local_key = "_pybind11_module_local_typeinfo";
+        constexpr auto *local_key = PYBIND11_MODULE_LOCAL_ID;
         const auto pytype = src.get_type();
         if (!hasattr(pytype, local_key))
             return false;
diff --git a/include/pybind11/detail/internals.h b/include/pybind11/detail/internals.h
index 73f34df5c..f1881fa47 100644
--- a/include/pybind11/detail/internals.h
+++ b/include/pybind11/detail/internals.h
@@ -62,6 +62,8 @@ struct overload_hash {
 };
 
 /// Internal data structure used to track registered instances and types.
+/// Whenever binary incompatible changes are made to this structure,
+/// `PYBIND11_INTERNALS_VERSION` must be incremented.
 struct internals {
     type_map<void *> registered_types_cpp; // std::type_index -> type_info
     std::unordered_map<PyTypeObject *, std::vector<type_info *>> registered_types_py; // PyTypeObject* -> base type_info(s)
@@ -83,6 +85,7 @@ struct internals {
 };
 
 /// Additional type information which does not fit into the PyTypeObject.
+/// Changes to this struct also require bumping `PYBIND11_INTERNALS_VERSION`.
 struct type_info {
     PyTypeObject *type;
     const std::type_info *cpptype;
@@ -107,8 +110,20 @@ struct type_info {
     bool module_local : 1;
 };
 
-#define PYBIND11_INTERNALS_ID "__pybind11_" \
-    PYBIND11_TOSTRING(PYBIND11_VERSION_MAJOR) "_" PYBIND11_TOSTRING(PYBIND11_VERSION_MINOR) "__"
+/// Tracks the `internals` and `type_info` ABI version independent of the main library version
+#define PYBIND11_INTERNALS_VERSION 1
+
+#if defined(WITH_THREAD)
+#  define PYBIND11_INTERNALS_KIND ""
+#else
+#  define PYBIND11_INTERNALS_KIND "_without_thread"
+#endif
+
+#define PYBIND11_INTERNALS_ID "__pybind11_internals_v" \
+    PYBIND11_TOSTRING(PYBIND11_INTERNALS_VERSION) PYBIND11_INTERNALS_KIND "__"
+
+#define PYBIND11_MODULE_LOCAL_ID "__pybind11_module_local_v" \
+    PYBIND11_TOSTRING(PYBIND11_INTERNALS_VERSION) PYBIND11_INTERNALS_KIND "__"
 
 /// Each module locally stores a pointer to the `internals` data. The data
 /// itself is shared among modules with the same `PYBIND11_INTERNALS_ID`.
diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index 5c78abee0..366ad81fc 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -870,7 +870,7 @@ protected:
         if (rec.module_local) {
             // Stash the local typeinfo and loader so that external modules can access it.
             tinfo->module_local_load = &type_caster_generic::local_load;
-            setattr(m_ptr, "_pybind11_module_local_typeinfo", capsule(tinfo));
+            setattr(m_ptr, PYBIND11_MODULE_LOCAL_ID, capsule(tinfo));
         }
     }