diff --git a/src/objects_container_impl_unittest.cpp b/src/objects_container_impl_unittest.cpp
index 63159d7a7..1a231a984 100644
--- a/src/objects_container_impl_unittest.cpp
+++ b/src/objects_container_impl_unittest.cpp
@@ -22,6 +22,8 @@
 
 #include "objects_container_impl.h"
 
+using namespace undo;
+
 TEST(ObjectsContainerImpl, AddObjectReturnsSameIdForSameObject)
 {
   ObjectsContainerImpl objs;