diff --git a/src/osx/core/bitmap.cpp b/src/osx/core/bitmap.cpp
index a4a0ac70b8..b08535ee65 100644
--- a/src/osx/core/bitmap.cpp
+++ b/src/osx/core/bitmap.cpp
@@ -1285,6 +1285,7 @@ wxImage wxBitmap::ConvertToImage() const
             r = ((color&0x0000FF00) >> 8) ;
             a = (color&0x000000FF);
 #endif
+            bool isMasked = false;
             if ( hasMask )
             {
                 if ( *maskp++ == 0x00 )
@@ -1292,6 +1293,7 @@ wxImage wxBitmap::ConvertToImage() const
                     r = MASK_RED ;
                     g = MASK_GREEN ;
                     b = MASK_BLUE ;
+                    isMasked = true;
                 }
                 else if ( r == MASK_RED && g == MASK_GREEN && b == MASK_BLUE )
                     b = MASK_BLUE_REPLACEMENT ;
@@ -1302,7 +1304,7 @@ wxImage wxBitmap::ConvertToImage() const
                 *alpha++ = a ;
 #if wxOSX_USE_PREMULTIPLIED_ALPHA
                 // this must be non-premultiplied data
-                if ( !hasMask && a != 0xFF && a!= 0 )
+                if ( !isMasked && a != 0xFF && a!= 0 )
                 {
                     r = r * 255 / a;
                     g = g * 255 / a;