diff --git a/libavcodec/raw.c b/libavcodec/raw.c
index a8a009bad1..91aba460ba 100644
--- a/libavcodec/raw.c
+++ b/libavcodec/raw.c
@@ -151,7 +151,8 @@ static int raw_init_encoder(AVCodecContext *avctx)
     avctx->coded_frame = (AVFrame *)avctx->priv_data;
     avctx->coded_frame->pict_type = FF_I_TYPE;
     avctx->coded_frame->key_frame = 1;
-    avctx->codec_tag = findFourCC(avctx->pix_fmt);
+    if(!avctx->codec_tag)
+        avctx->codec_tag = findFourCC(avctx->pix_fmt);
     return 0;
 }