diff --git a/mac_build/boinc.pbproj/project.pbxproj b/mac_build/boinc.pbproj/project.pbxproj
index 7855fad852..69bee242e4 100755
--- a/mac_build/boinc.pbproj/project.pbxproj
+++ b/mac_build/boinc.pbproj/project.pbxproj
@@ -1627,7 +1627,7 @@
 				F54FF8A7029F2FAA012012A7,
 			);
 			buildSettings = {
-				OTHER_CFLAGS = "-DHAVE_DIRENT_H -DHAVE_SYS_TIME_H -DHAVE_SYS_RESOURCE_H";
+				OTHER_CFLAGS = "-DHAVE_DIRENT_H -DHAVE_SYS_TIME_H -DHAVE_SYS_RESOURCE_H -DHAVE_UNISTD_H ";
 				OTHER_LDFLAGS = "";
 				OTHER_REZFLAGS = "";
 				PRODUCT_NAME = concat;