--- glyphs.c~	Wed May 03 10:20:35 2000
+++ glyphs.c	Thu May 04 09:37:03 2000
@@ -688,6 +688,11 @@
   IMAGE_INSTANCE_LAYOUT_CHANGED (p) = 0;
   IMAGE_INSTANCE_DIRTYP (p) = 0;
 
+  assert (XIMAGE_INSTANCE_HEIGHT (ii) 
+	  != IMAGE_UNSPECIFIED_GEOMETRY
+	  && XIMAGE_INSTANCE_WIDTH (ii) 
+	  != IMAGE_UNSPECIFIED_GEOMETRY);
+
   ERROR_CHECK_IMAGE_INSTANCE (ii);
 
   RETURN_UNGCPRO (ii);