diff --git a/core/bench_test.go b/core/bench_test.go
index 7dd4839b4d..3006e55131 100644
--- a/core/bench_test.go
+++ b/core/bench_test.go
@@ -160,7 +160,7 @@ func genTxRing(naccounts int) func(int, *BlockGen) {
 
 // genUncles generates blocks with two uncle headers.
 func genUncles(i int, gen *BlockGen) {
-	if i >= 6 {
+	if i >= 7 {
 		b2 := gen.PrevBlock(i - 6).Header()
 		b2.Extra = []byte("foo")
 		gen.AddUncle(b2)