diff --git a/src/mac/carbon/overlay.cpp b/src/mac/carbon/overlay.cpp
index f1e2e046ee..b2786c75da 100644
--- a/src/mac/carbon/overlay.cpp
+++ b/src/mac/carbon/overlay.cpp
@@ -139,6 +139,7 @@ void wxOverlayImpl::BeginDrawing( wxWindowDC* dc)
 void wxOverlayImpl::EndDrawing( wxWindowDC* dc)
 {
     dc->SetGraphicsContext(NULL);
+    CGContextSynchronize( m_overlayContext );
 }
 
 void wxOverlayImpl::Clear(wxWindowDC* dc)