2 files changed, 18 insertions, 2 deletions
diff --git a/src/net/http/http.go b/src/net/http/http.go
index 101799f574..9b81654fcc 100644
--- a/src/net/http/http.go
+++ b/src/net/http/http.go
@@ -86,14 +86,20 @@ func hexEscapeNonASCII(s string) string {
 		return s
 	}
 	b := make([]byte, 0, newLen)
+	var pos int
 	for i := 0; i < len(s); i++ {
 		if s[i] >= utf8.RuneSelf {
+			if pos < i {
+				b = append(b, s[pos:i]...)
+			}
 			b = append(b, '%')
 			b = strconv.AppendInt(b, int64(s[i]), 16)
-		} else {
-			b = append(b, s[i])
+			pos = i + 1
 		}
 	}
+	if pos < len(s) {
+		b = append(b, s[pos:]...)
+	}
 	return string(b)
 }
 
diff --git a/src/net/http/http_test.go b/src/net/http/http_test.go
index 0d92fe5f96..1c9fb33b69 100644
--- a/src/net/http/http_test.go
+++ b/src/net/http/http_test.go
@@ -218,3 +218,13 @@ func TestNoUnicodeStrings(t *testing.T) {
 		t.Fatal(err)
 	}
 }
+
+const redirectURL = "/thisaredirect细雪withasciilettersのけぶabcdefghijk.html"
+
+func BenchmarkHexEscapeNonASCII(b *testing.B) {
+	b.ReportAllocs()
+
+	for i := 0; i < b.N; i++ {
+		hexEscapeNonASCII(redirectURL)
+	}
+}