diff --git a/core/unix/ksynch_macos.c b/core/unix/ksynch_macos.c
index a00e167b5ce..09089030c29 100644
--- a/core/unix/ksynch_macos.c
+++ b/core/unix/ksynch_macos.c
@@ -41,6 +41,7 @@
  */
 
 #include "../globals.h"
+#include <errno.h>
 #include "ksynch.h"
 
 #include <mach/mach.h>