diff --git a/man7/sigevent.7 b/man7/sigevent.7
index 745c6a9a7..9d8ac6a2e 100644
--- a/man7/sigevent.7
+++ b/man7/sigevent.7
@@ -28,6 +28,7 @@
 sigevent \- structure for notification from asynchronous routines
 .SH SYNOPSIS
 .nf
+#include <signal.h>
 
 union sigval {          /* Data passed with notification */
     int     sival_int;         /* Integer value */