diff --git a/src/testing/benchmark.go b/src/testing/benchmark.go
index 53c7fc7b1..2dc59b72f 100644
--- a/src/testing/benchmark.go
+++ b/src/testing/benchmark.go
@@ -500,6 +500,10 @@ func (b *B) RunParallel(body func(*PB)) {
 	return
 }
 
+func (b *B) Loop() bool {
+	panic("unimplemented: testing.B.Loop")
+}
+
 // Benchmark benchmarks a single function. It is useful for creating
 // custom benchmarks that do not use the "go test" command.
 //