diff --git a/src/cmd/compile/internal/ssa/check.go b/src/cmd/compile/internal/ssa/check.go
index e4b8cb05f4..f1d3857f88 100644
--- a/src/cmd/compile/internal/ssa/check.go
+++ b/src/cmd/compile/internal/ssa/check.go
@@ -338,7 +338,7 @@ func checkFunc(f *Func) {
 
 // domCheck reports whether x dominates y (including x==y).
 func domCheck(f *Func, sdom sparseTree, x, y *Block) bool {
-	if !sdom.isAncestorEq(y, f.Entry) {
+	if !sdom.isAncestorEq(f.Entry, y) {
 		// unreachable - ignore
 		return true
 	}