diff --git a/util/file_test.go b/util/file_test.go
index 9691975..f94d4ac 100644
--- a/util/file_test.go
+++ b/util/file_test.go
@@ -21,7 +21,7 @@ func TestNWriter(t *testing.T) {
 	}
 
 	if n := int64(len(msg)); nw.N != n {
-		t.Errorf("Expected %d bytes, but counted %d", n, nw.N)
+		t.Errorf("Expected %d bytes, but counted %d.", n, nw.N)
 	}
 
 	if out := buf.Bytes(); !bytes.Equal(msg, out) {