diff --git a/portability/unistd.h b/portability/unistd.h
index 4d0cef8..f87ff71 100644
--- a/portability/unistd.h
+++ b/portability/unistd.h
@@ -3,3 +3,8 @@
 #ifdef NEED_PIPE2
 int pipe2(int pipefd[2], int flags);
 #endif
+
+#ifdef __APPLE__
+# include <crt_externs.h>
+# define environ (*_NSGetEnviron())
+#endif