diff --git a/src/posix/cocoa/st_start.mm b/src/posix/cocoa/st_start.mm
index a1db95a0b..36582c64b 100644
--- a/src/posix/cocoa/st_start.mm
+++ b/src/posix/cocoa/st_start.mm
@@ -31,6 +31,8 @@
  **
  */
 
+#include <unistd.h>
+
 #import <Foundation/NSRunLoop.h>
 
 #include "c_cvars.h"