diff --git a/sim/cris/ChangeLog b/sim/cris/ChangeLog
index 06ca4e4132b..1b4a5fe3366 100644
--- a/sim/cris/ChangeLog
+++ b/sim/cris/ChangeLog
@@ -1,3 +1,7 @@
+2021-05-23  Mike Frysinger  <vapier@gentoo.org>
+
+	* sim-if.c: Include unistd.h.
+
 2021-05-17  Mike Frysinger  <vapier@gentoo.org>
 
 	* sim-main.h (struct sim_state): Delete.
diff --git a/sim/cris/sim-if.c b/sim/cris/sim-if.c
index 15a4018b5b7..cea499d1daa 100644
--- a/sim/cris/sim-if.c
+++ b/sim/cris/sim-if.c
@@ -30,6 +30,7 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
 #include "sim-main.h"
 #include <stdlib.h>
 #include <errno.h>
+#include <unistd.h>
 #include "sim-options.h"
 #include "dis-asm.h"
 #include "environ.h"