diff --git a/podofo_config.h.in b/podofo_config.h.in
index fea9ada..a813c7b 100644
--- a/podofo_config.h.in
+++ b/podofo_config.h.in
@@ -59,3 +59,10 @@
 #cmakedefine PODOFO_HAVE_OPENSSL_NO_RC4
 #cmakedefine PODOFO_HAVE_LIBIDN
 #cmakedefine PODOFO_HAVE_UNISTRING_LIB
+
+/* Fix build for MacOS 10.13 */
+#if defined(__APPLE__) && !defined(__IOS__)
+#cmakedefine01 HAVE_UNISTD_H
+#else
+#cmakedefine HAVE_UNISTD_H
+#endif
