diff --git a/src/cmd/compile/internal/ssa/fuse.go b/src/cmd/compile/internal/ssa/fuse.go
index 1f826cd25e2..ce759cdec1d 100644
--- a/src/cmd/compile/internal/ssa/fuse.go
+++ b/src/cmd/compile/internal/ssa/fuse.go
@@ -65,7 +65,7 @@ func fuseBlockIf(b *Block) bool {
 		b.Fatalf("invalid predecessors")
 	}
 	for _, v := range ss.Values {
-		if v.Op == OpPhi && v.Args[i0] != v.Args[i1] {
+		if v.Op == OpPhi && v.Uses > 0 && v.Args[i0] != v.Args[i1] {
 			return false
 		}
 	}