diff --git a/websh.c b/websh.c
index 6263a16..9d62820 100644
--- a/websh.c
+++ b/websh.c
@@ -9,6 +9,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <unistd.h>
+#include <assert.h>
 
 #include <errno.h>
 #include <signal.h>