diff --git a/src/ecmascript/spidermonkey/heartbeat.c b/src/ecmascript/spidermonkey/heartbeat.c
index f71206a0..4eaed4db 100644
--- a/src/ecmascript/spidermonkey/heartbeat.c
+++ b/src/ecmascript/spidermonkey/heartbeat.c
@@ -5,6 +5,7 @@
 #endif
 
 #include <sys/time.h>    /* setitimer(2) */
+#include <signal.h>
 
 #include "elinks.h"