diff --git a/gcc/cp/module.cc b/gcc/cp/module.cc
index 8aab9ea0bae..4e91fa6e052 100644
--- a/gcc/cp/module.cc
+++ b/gcc/cp/module.cc
@@ -7649,6 +7649,19 @@ trees_in::install_entity (tree decl)
       gcc_checking_assert (!existed);
       slot = ident;
     }
+  else if (state->is_partition ())
+    {
+      /* The decl is already in the entity map, but we see it again now from a
+	 partition: we want to overwrite if the original decl wasn't also from
+	 a (possibly different) partition.  Otherwise, for things like template
+	 instantiations, make_dependency might not realise that this is also
+	 provided from a partition and should be considered part of this module
+	 (and thus always emitted into the primary interface's CMI).  */
+      unsigned *slot = entity_map->get (DECL_UID (decl));
+      module_state *imp = import_entity_module (*slot);
+      if (!imp->is_partition ())
+	*slot = ident;
+    }
 
   return true;
 }
diff --git a/gcc/testsuite/g++.dg/modules/pr99377-3_a.H b/gcc/testsuite/g++.dg/modules/pr99377-3_a.H
new file mode 100644
index 00000000000..580a7631ae1
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/pr99377-3_a.H
@@ -0,0 +1,17 @@
+// { dg-additional-options "-fmodule-header" }
+// { dg-module-cmi {} }
+
+template<typename>
+struct Widget
+{
+  Widget (int) { }
+
+  bool First() const { return true; }
+
+  bool Second () const { return true;}
+};
+
+inline void Frob (const Widget<int>& w) noexcept
+{
+  w.First ();
+}
diff --git a/gcc/testsuite/g++.dg/modules/pr99377-3_b.C b/gcc/testsuite/g++.dg/modules/pr99377-3_b.C
new file mode 100644
index 00000000000..5cbce7b3544
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/pr99377-3_b.C
@@ -0,0 +1,10 @@
+// { dg-additional-options "-fmodules-ts" }
+// { dg-module-cmi Foo:check }
+
+export module Foo:check;
+import "pr99377-3_a.H";
+
+export inline bool Check (const Widget<int>& w)
+{
+  return w.Second ();
+}
diff --git a/gcc/testsuite/g++.dg/modules/pr99377-3_c.C b/gcc/testsuite/g++.dg/modules/pr99377-3_c.C
new file mode 100644
index 00000000000..fa7c24203bd
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/pr99377-3_c.C
@@ -0,0 +1,5 @@
+// { dg-additional-options "-fmodules-ts" }
+// { dg-module-cmi Foo }
+
+export module Foo;
+export import :check;
diff --git a/gcc/testsuite/g++.dg/modules/pr99377-3_d.C b/gcc/testsuite/g++.dg/modules/pr99377-3_d.C
new file mode 100644
index 00000000000..cb1f28321b1
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/pr99377-3_d.C
@@ -0,0 +1,8 @@
+// { dg-module-do link }
+// { dg-additional-options "-fmodules-ts" }
+
+import Foo;
+
+int main() {
+  return Check(0) ? 0 : 1;
+}