diff --git a/tmate-ssh-server.c b/tmate-ssh-server.c
index 25c7878c..b96ba119 100644
--- a/tmate-ssh-server.c
+++ b/tmate-ssh-server.c
@@ -6,6 +6,7 @@
 #include <sys/wait.h>
 #include <ctype.h>
 #include <stdio.h>
+#include <signal.h>
 #include <event.h>
 #include <arpa/inet.h>
 #ifndef IPPROTO_TCP