diff --git a/gdk/gdkpixbuf-drawable.c b/gdk/gdkpixbuf-drawable.c
index 2e3de8c8fb..0647e3c00d 100644
--- a/gdk/gdkpixbuf-drawable.c
+++ b/gdk/gdkpixbuf-drawable.c
@@ -119,6 +119,7 @@ gdk_cairo_format_for_content (cairo_content_t content)
     {
     case CAIRO_CONTENT_COLOR:
       return CAIRO_FORMAT_RGB24;
+    case CAIRO_CONTENT_ALPHA:
       return CAIRO_FORMAT_A8;
     case CAIRO_CONTENT_COLOR_ALPHA:
     default: