diff --git a/panda/src/osxdisplay/osxGraphicsPipe.cxx b/panda/src/osxdisplay/osxGraphicsPipe.cxx
index 8c66cfb317..b362d1fbb0 100644
--- a/panda/src/osxdisplay/osxGraphicsPipe.cxx
+++ b/panda/src/osxdisplay/osxGraphicsPipe.cxx
@@ -68,6 +68,19 @@ pipe_constructor() {
   return new osxGraphicsPipe;
 }
 
+////////////////////////////////////////////////////////////////////
+//     Function: osxGraphicsPipe::get_preferred_window_thread
+//       Access: Public, Virtual
+//  Description: Returns an indication of the thread in which this
+//               GraphicsPipe requires its window processing to be
+//               performed: typically either the app thread (e.g. X)
+//               or the draw thread (Windows).
+////////////////////////////////////////////////////////////////////
+GraphicsPipe::PreferredWindowThread 
+osxGraphicsPipe::get_preferred_window_thread() const {
+  return PWT_app;
+}
+
 ////////////////////////////////////////////////////////////////////
 //     Function: osxGraphicsPipe::create_cg_image
 //       Access: Public, Static
@@ -120,6 +133,11 @@ create_cg_image(const PNMImage &pnm_image) {
     has_alpha = true;
     is_grayscale = false;
     break;
+
+  case PNMImage::CT_invalid:
+    // Shouldn't get here.
+    nassertr(false, NULL);
+    break;
   }
   nassertr(color_space_name != NULL, NULL);
 
diff --git a/panda/src/osxdisplay/osxGraphicsPipe.h b/panda/src/osxdisplay/osxGraphicsPipe.h
index b12c8136b0..d6deb8ef7b 100644
--- a/panda/src/osxdisplay/osxGraphicsPipe.h
+++ b/panda/src/osxdisplay/osxGraphicsPipe.h
@@ -37,6 +37,7 @@ public:
 
   virtual string get_interface_name() const;
   static PT(GraphicsPipe) pipe_constructor();
+  virtual PreferredWindowThread get_preferred_window_thread() const;
 
   static CGImageRef create_cg_image(const PNMImage &pnm_image);