diff --git a/src/common/sizer.cpp b/src/common/sizer.cpp
index 08045e5b41..18c06c0da4 100644
--- a/src/common/sizer.cpp
+++ b/src/common/sizer.cpp
@@ -89,6 +89,8 @@ WX_DEFINE_EXPORTED_LIST( wxSizerItemList )
 // ----------------------------------------------------------------------------
 
 // check for flags conflicts
+#if wxDEBUG_LEVEL
+
 static const int SIZER_FLAGS_MASK =
     wxADD_FLAG(wxCENTRE,
     wxADD_FLAG(wxHORIZONTAL,
@@ -110,6 +112,8 @@ static const int SIZER_FLAGS_MASK =
     wxADD_FLAG(wxSHAPED,
     0))))))))))))))))));
 
+#endif // wxDEBUG_LEVEL
+
 #define ASSERT_VALID_SIZER_FLAGS(f)  wxASSERT_VALID_FLAGS(f, SIZER_FLAGS_MASK)