diff --git a/libavformat/mpegenc.c b/libavformat/mpegenc.c
index ca9d481978..83a628a5fb 100644
--- a/libavformat/mpegenc.c
+++ b/libavformat/mpegenc.c
@@ -299,9 +299,9 @@ static int mpeg_mux_init(AVFormatContext *ctx)
     s->packet_number = 0;
     s->is_vcd =   (ENABLE_MPEG1VCD_MUXER  && ctx->oformat == &mpeg1vcd_muxer);
     s->is_svcd =  (ENABLE_MPEG2SVCD_MUXER && ctx->oformat == &mpeg2svcd_muxer);
-    s->is_mpeg2 = (ENABLE_MPEG2VOB_MUXER  && ctx->oformat == &mpeg2vob_muxer ||
-                   ENABLE_MPEG2DVD_MUXER  && ctx->oformat == &mpeg2dvd_muxer ||
-                   ENABLE_MPEG2SVCD_MUXER && ctx->oformat == &mpeg2svcd_muxer);
+    s->is_mpeg2 = ((ENABLE_MPEG2VOB_MUXER  && ctx->oformat == &mpeg2vob_muxer) ||
+                   (ENABLE_MPEG2DVD_MUXER  && ctx->oformat == &mpeg2dvd_muxer) ||
+                   (ENABLE_MPEG2SVCD_MUXER && ctx->oformat == &mpeg2svcd_muxer));
     s->is_dvd =   (ENABLE_MPEG2DVD_MUXER  && ctx->oformat == &mpeg2dvd_muxer);
 
     if(ctx->packet_size)