diff --git a/server/nf_callbacks.c b/server/nf_callbacks.c
index 01c9a11..07b0127 100644
--- a/server/nf_callbacks.c
+++ b/server/nf_callbacks.c
@@ -25,6 +25,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <signal.h>
 #include <sys/types.h>
 #include <sys/wait.h>
 #include <unistd.h>