diff --git a/tester/multipart-tester.cpp b/tester/multipart-tester.cpp
index 1c54389f2..663b114f4 100644
--- a/tester/multipart-tester.cpp
+++ b/tester/multipart-tester.cpp
@@ -96,6 +96,8 @@ static void chat_message_multipart_modifier_base(bool first_file_transfer, bool
 			BC_ASSERT_STRING_EQUAL(content, "Hello part 2");
 	}
 
+	marieRoom.reset(); // Avoid bad weak ptr when the core is destroyed below this line.
+
 	linphone_core_manager_destroy(marie);
 	linphone_core_manager_destroy(pauline);
 }