diff --git a/libavcodec/mjpegdec.c b/libavcodec/mjpegdec.c
index 166c22306f..07883e2b72 100644
--- a/libavcodec/mjpegdec.c
+++ b/libavcodec/mjpegdec.c
@@ -279,7 +279,7 @@ int ff_mjpeg_decode_sof(MJpegDecodeContext *s)
         return -1;
     }
 
-    if(s->v_max==1 && s->h_max==1 && s->lossless==1) s->rgb=1;
+    if(s->v_max==1 && s->h_max==1 && s->lossless==1 && nb_components==3) s->rgb=1;
 
     /* if different size, realloc/alloc picture */
     /* XXX: also check h_count and v_count */