diff --git a/ChangeLog b/ChangeLog
index f9157d179b..95b7e2a59e 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+2019-02-03  Aurelien Jarno  <aurelien@aurel32.net>
+
+	* stdlib/isomac.c: Include <unistd.h>.
+
 2018-11-07  Florian Weimer  <fweimer@redhat.com>
 
 	Implement TEST_COMPARE_STRING.
diff --git a/stdlib/isomac.c b/stdlib/isomac.c
index 0873eaa505..439b000734 100644
--- a/stdlib/isomac.c
+++ b/stdlib/isomac.c
@@ -74,6 +74,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <unistd.h>
 
 #define HEADER_MAX          256