diff --git a/mkvmuxer/mkvmuxerutil.cc b/mkvmuxer/mkvmuxerutil.cc
index bd98b11..355d4e2 100644
--- a/mkvmuxer/mkvmuxerutil.cc
+++ b/mkvmuxer/mkvmuxerutil.cc
@@ -10,6 +10,7 @@
 
 #ifdef __ANDROID__
 #include <fcntl.h>
+#include <unistd.h>
 #endif
 
 #include <cassert>