diff --git a/tests/asserthelper.h b/tests/asserthelper.h
index ebd16c2d3e..74ca91242c 100644
--- a/tests/asserthelper.h
+++ b/tests/asserthelper.h
@@ -26,10 +26,10 @@ namespace
         unsigned char m_value;
     };
 
-    std::ostream& operator<<(std::ostream& os, const ColourChannel& cc);
-
 } // anonymous namespace
 
+std::ostream& operator<<(std::ostream& os, const ColourChannel& cc);
+
 // this operator is needed to use CPPUNIT_ASSERT_EQUAL with wxColour objects
 std::ostream& operator<<(std::ostream& os, const wxColour& c);