diff --git a/config.h.in b/config.h.in
index b634b53ca..f6850c8bc 100644
--- a/config.h.in
+++ b/config.h.in
@@ -3,7 +3,11 @@
 
 /* Include files */
 #cmakedefine HAVE_FCNTL_H
+#if defined(__APPLE__) && !defined(__IOS__)
+#cmakedefine01 HAVE_UNISTD_H
+#else
 #cmakedefine HAVE_UNISTD_H
+#endif
 #cmakedefine HAVE_INTTYPES_H
 #cmakedefine HAVE_SYS_MODEM_H
 #cmakedefine HAVE_SYS_FILIO_H