diff --git a/src/bufio/bufio_test.go b/src/bufio/bufio_test.go
index c829d2b064..34d70312f7 100644
--- a/src/bufio/bufio_test.go
+++ b/src/bufio/bufio_test.go
@@ -550,7 +550,7 @@ func TestWriter(t *testing.T) {
 				t.Errorf("%s: %d bytes written", context, len(written))
 			}
 			for l := 0; l < len(written); l++ {
-				if written[i] != data[i] {
+				if written[l] != data[l] {
 					t.Errorf("wrong bytes written")
 					t.Errorf("want=%q", data[0:len(written)])
 					t.Errorf("have=%q", written)