diff --git a/src/osx/cocoa/nonownedwnd.mm b/src/osx/cocoa/nonownedwnd.mm
index b21d2d2e14..a1084ccc15 100644
--- a/src/osx/cocoa/nonownedwnd.mm
+++ b/src/osx/cocoa/nonownedwnd.mm
@@ -769,12 +769,6 @@ long style, long extraStyle, const wxString& WXUNUSED(name) )
 
     [m_macWindow setDelegate:controller];
     [controller addObservers:m_macWindow];
-
-    if ( ( style & wxFRAME_SHAPED) )
-    {
-        [m_macWindow setOpaque:NO];
-        [m_macWindow setAlphaValue:1.0];
-    }
     
     if ( !(style & wxFRAME_TOOL_WINDOW) )
         [m_macWindow setHidesOnDeactivate:NO];
diff --git a/src/osx/cocoa/window.mm b/src/osx/cocoa/window.mm
index eaddbc7cad..b32f5aef66 100644
--- a/src/osx/cocoa/window.mm
+++ b/src/osx/cocoa/window.mm
@@ -3136,7 +3136,14 @@ void wxWidgetCocoaImpl::SetBackgroundColour( const wxColour &col )
 
     if ( [targetView respondsToSelector:@selector(setBackgroundColor:) ] )
     {
-        [targetView setBackgroundColor: col.OSXGetNSColor()];
+        wxWindow* peer = GetWXPeer();
+        if ( peer->GetBackgroundStyle() != wxBG_STYLE_TRANSPARENT )
+        {
+            wxTopLevelWindow* toplevel = wxDynamicCast(peer,wxTopLevelWindow);
+
+            if ( toplevel == NULL || toplevel->GetShape().IsEmpty() )
+                [targetView setBackgroundColor: col.OSXGetNSColor()];
+        }
     }
 }
 
@@ -3147,6 +3154,8 @@ bool wxWidgetCocoaImpl::SetBackgroundStyle( wxBackgroundStyle style )
     if ( [m_osxView respondsToSelector:@selector(setOpaque:) ] )
     {
         [m_osxView setOpaque: opaque];
+        if ( style == wxBG_STYLE_TRANSPARENT )
+            [m_osxView setBackgroundColor:[NSColor clearColor]];
     }
     
     return true ;
diff --git a/src/osx/nonownedwnd_osx.cpp b/src/osx/nonownedwnd_osx.cpp
index d43a4eba65..cbc20eda73 100644
--- a/src/osx/nonownedwnd_osx.cpp
+++ b/src/osx/nonownedwnd_osx.cpp
@@ -254,17 +254,13 @@ wxPoint wxNonOwnedWindow::GetClientAreaOrigin() const
 
 bool wxNonOwnedWindow::SetBackgroundColour(const wxColour& c )
 {
+    if ( !wxWindow::SetBackgroundColour(c) && m_hasBgCol )
+        return false ;
+    
     // only set the native background color if the toplevel window's
     // background is not supposed to be transparent, otherwise the
     // transparency is lost
-    if( GetBackgroundStyle() == wxBG_STYLE_TRANSPARENT ||
-       (GetWindowStyle() & wxFRAME_SHAPED) )
-        return false;
-
-    if ( !wxWindow::SetBackgroundColour(c) && m_hasBgCol )
-        return false ;
-
-    if ( GetBackgroundStyle() != wxBG_STYLE_CUSTOM )
+    if ( GetBackgroundStyle() != wxBG_STYLE_PAINT && GetBackgroundStyle() != wxBG_STYLE_TRANSPARENT)
     {
         if ( m_nowpeer )
             return m_nowpeer->SetBackgroundColour(c);
@@ -522,6 +518,10 @@ bool wxNonOwnedWindow::DoSetRegionShape(const wxRegion& region)
 {
     m_shape = region;
 
+    // set the native content view to transparency, this is an implementation detail
+    // no reflected in the wx BackgroundStyle
+    GetPeer()->SetBackgroundStyle(wxBG_STYLE_TRANSPARENT);
+
     return m_nowpeer->SetShape(region);
 }