diff --git a/libavformat/matroskaenc.c b/libavformat/matroskaenc.c
index c1b6057251..03302ecf3f 100644
--- a/libavformat/matroskaenc.c
+++ b/libavformat/matroskaenc.c
@@ -524,7 +524,7 @@ static int mkv_write_header(AVFormatContext *s)
     if (strlen(s->title))
         put_ebml_string(pb, MATROSKA_ID_TITLE, s->title);
     if (!(s->streams[0]->codec->flags & CODEC_FLAG_BITEXACT)) {
-        put_ebml_string(pb, MATROSKA_ID_MUXINGAPP, LIBAVFORMAT_IDENT);
+        put_ebml_string(pb, MATROSKA_ID_MUXINGAPP , LIBAVFORMAT_IDENT);
         put_ebml_string(pb, MATROSKA_ID_WRITINGAPP, LIBAVFORMAT_IDENT);
     }
     // XXX: segment UID