diff --git a/libavformat/rtsp.c b/libavformat/rtsp.c
index 47378146fe..5100c978e6 100644
--- a/libavformat/rtsp.c
+++ b/libavformat/rtsp.c
@@ -202,6 +202,8 @@ static void sdp_parse_fmtp_config(AVCodecContext *codec, char *attr, char *value
             if (!strcmp(attr, "config")) {
                 /* decode the hexa encoded parameter */
                 int len = hex_to_data(NULL, value);
+                if (codec->extradata)
+                    av_free(codec->extradata);
                 codec->extradata = av_mallocz(len + FF_INPUT_BUFFER_PADDING_SIZE);
                 if (!codec->extradata)
                     return;