diff --git a/level.go b/level.go
old mode 100644
new mode 100755
diff --git a/level_test.go b/level_test.go
old mode 100644
new mode 100755
diff --git a/logb.go b/logb.go
old mode 100644
new mode 100755
index 091b37b..efdce2c
--- a/logb.go
+++ b/logb.go
@@ -85,6 +85,9 @@ func logf(lvl Level, form string, args ...interface{}) {
 		return
 	}
 	form = fmt.Sprintf("[%v] %s\n", lvl.String()[:3], form)
-	fmt.Fprintf(os.Stderr, "stderr: "+form, args...)
-	fmt.Fprintf(writer, form, args...)
+	if writer != os.Stderr {
+		fmt.Fprintf(writer, form, args...)
+	} else {
+		fmt.Fprintf(os.Stderr, form, args...)
+	}
 }
diff --git a/logb_test.go b/logb_test.go
old mode 100644
new mode 100755