diff --git a/src/mac/carbon/colour.cpp b/src/mac/carbon/colour.cpp
index d752b70530..4af845a7e4 100644
--- a/src/mac/carbon/colour.cpp
+++ b/src/mac/carbon/colour.cpp
@@ -66,6 +66,7 @@ void wxColour::FromRGBColor( WXCOLORREF* color )
     m_red = col->red >> 8;
     m_blue = col->blue >> 8;
     m_green = col->green >> 8;
+    m_alpha = 255;
 }
 
 wxColour& wxColour::operator=(const RGBColor& col)