diff --git a/signal.c b/signal.c
index ce5b462..5e73f8f 100644
--- a/signal.c
+++ b/signal.c
@@ -1500,6 +1500,7 @@
 		tcp->u_arg[0] = 0;
 		sp = regs.regs[29];
 		if (umove(tcp, sp, &si) < 0)
+			return 0;
 		tcp->u_arg[0] = 1;
 		tcp->u_arg[1] = si.si_mask;
 	} else {