diff --git a/test/support/nasty_containers.hpp b/test/support/nasty_containers.hpp
index 292181b13..b9ef5a6a7 100644
--- a/test/support/nasty_containers.hpp
+++ b/test/support/nasty_containers.hpp
@@ -287,7 +287,7 @@ public:
      nasty_mutex() _NOEXCEPT {}
      ~nasty_mutex() {}
 
-	nasty_mutex *operator& ()   { assert(false); }
+	nasty_mutex *operator& ()   { assert(false); return nullptr; }
 	template <typename T>
 	void operator, (const T &) { assert(false); }