diff --git a/src/runtime/sys_plan9_amd64.s b/src/runtime/sys_plan9_amd64.s
index d0586a5ae9..36d2d97e20 100644
--- a/src/runtime/sys_plan9_amd64.s
+++ b/src/runtime/sys_plan9_amd64.s
@@ -194,7 +194,7 @@ TEXT runtime·sigtramp(SB),NOSPLIT,$0
 	MOVQ	BP, SP
 
 	// make room for args and g
-	SUBQ	$40, SP
+	SUBQ	$128, SP
 
 	// save g
 	MOVQ	g(AX), BP