diff --git a/procname.c b/procname.c
index ac56bb48..b2cba1c2 100644
--- a/procname.c
+++ b/procname.c
@@ -18,6 +18,7 @@
 
 #include <sys/param.h>	/* MAXCOMLEN */
 #include <sys/types.h>
+#include <sys/signal.h>
 #include <sys/proc.h>
 #include <sys/sysctl.h>
 #include <sys/stat.h>