diff --git a/cmds/stagefright/muxer.cpp b/cmds/stagefright/muxer.cpp
index 0d04760..36fa3b5 100644
--- a/cmds/stagefright/muxer.cpp
+++ b/cmds/stagefright/muxer.cpp
@@ -143,7 +143,7 @@
 
         ssize_t newTrackIndex = muxer->addTrack(format);
         if (newTrackIndex < 0) {
-            fprintf(stderr, "%s track (%d) unsupported by muxer\n",
+            fprintf(stderr, "%s track (%zu) unsupported by muxer\n",
                     isAudio ? "audio" : "video",
                     i);
         } else {