diff --git a/os/ospoll.c b/os/ospoll.c
index 8102ebd989..70ed71f4f7 100644
--- a/os/ospoll.c
+++ b/os/ospoll.c
@@ -22,6 +22,7 @@
 
 #include <dix-config.h>
 
+#include <assert.h>
 #include <string.h>
 #include <stdlib.h>
 #include <unistd.h>