diff --git a/libswscale/swscale.c b/libswscale/swscale.c
index 05ee8a4d91..eaec1dd82c 100644
--- a/libswscale/swscale.c
+++ b/libswscale/swscale.c
@@ -2672,7 +2672,7 @@ static int swScale(SwsContext *c, const uint8_t* src[],
         }
     }
 
-    if ((dstFormat == PIX_FMT_YUVA420P) && !alpPixBuf)
+    if (isPlanar(dstFormat) && isALPHA(dstFormat) && !alpPixBuf)
         fillPlane(dst[3], dstStride[3], dstW, dstY-lastDstY, lastDstY, 255);
 
 #if HAVE_MMX2