diff --git a/ruamoko/qwaq/builtins/graphics.c b/ruamoko/qwaq/builtins/graphics.c
index e31aa1d27..1f408344c 100644
--- a/ruamoko/qwaq/builtins/graphics.c
+++ b/ruamoko/qwaq/builtins/graphics.c
@@ -303,7 +303,10 @@ generate_colormap (void)
 		memcpy (colors[i][224], colors[31][224], 32 * 3);
 	}
 	tex_t     *cmap = ConvertImage (&tex, default_palette[0]);
-	memcpy (default_colormap, cmap->data, sizeof (default_colormap));
+	// the colormap has an extra byte indicating the number of fullbright
+	// entries, but that byte is not in the image, so don't try to copy it,
+	// thus the - 1
+	memcpy (default_colormap, cmap->data, sizeof (default_colormap) - 1);
 	free (cmap);
 }