diff --git a/st.c b/st.c
index 78cb9b7..0f4593e 100644
--- a/st.c
+++ b/st.c
@@ -967,7 +967,7 @@ ttyresize(int tw, int th)
 }
 
 void
-ttyhangup()
+ttyhangup(void)
 {
 	/* Send SIGHUP to shell */
 	kill(pid, SIGHUP);