diff --git a/tests/libs/namespaces_root.cpp b/tests/libs/namespaces_root.cpp
index b0006c7..a551673 100644
--- a/tests/libs/namespaces_root.cpp
+++ b/tests/libs/namespaces_root.cpp
@@ -20,6 +20,14 @@
 extern "C" const char* g_private_extern_string;
 extern "C" const char* g_public_extern_string;
 
+// This is resolved only if public library is in the same namespace as
+// the root one. It should remain unresolved if looking up for public library
+// crosses namespace boundary.
+//
+// Defined in libnstest_public_internal.so on which libnstest_public.so
+// depends on
+extern "C" const char* __attribute__((weak)) internal_extern_string();
+
 bool g_dlopened = false;
 
 extern "C" const char* ns_get_local_string() {
@@ -34,6 +42,14 @@
   return g_public_extern_string;
 }
 
+extern "C" const char* ns_get_internal_extern_string() {
+  if (internal_extern_string != nullptr) {
+    return internal_extern_string();
+  } else {
+    return nullptr;
+  }
+}
+
 extern "C" const char* ns_get_dlopened_string() {
   void* handle = dlopen("libnstest_dlopened.so", RTLD_NOW | RTLD_GLOBAL);
   if (handle == nullptr) {