diff --git a/include/wx/matrix.h b/include/wx/matrix.h
index 0cbeb2ba0d..018362a171 100644
--- a/include/wx/matrix.h
+++ b/include/wx/matrix.h
@@ -122,8 +122,11 @@ public:
     //!code:           | -1     0      0 |
     //!code: matrix' = |  0    -1      0 | x matrix
     //!code:           |  0     0      1 |
+#if defined(__WXPM__)
+    wxTransformMatrix&  Mirror(bool x=TRUE, bool y=FALSE);
+#else
     wxTransformMatrix&  Mirror(bool x=true, bool y=false);
-
+#endif
     // Translate by dx, dy:
     //!ex:
     //!code:           | 1  0 dx |