diff --git a/src/strconv/quote.go b/src/strconv/quote.go
index 40d0667551..a37a309f26 100644
--- a/src/strconv/quote.go
+++ b/src/strconv/quote.go
@@ -6,15 +6,19 @@
 
 package strconv
 
-import (
-	"unicode/utf8"
-)
+import "unicode/utf8"
 
 const lowerhex = "0123456789abcdef"
 
 func quoteWith(s string, quote byte, ASCIIonly, graphicOnly bool) string {
-	var runeTmp [utf8.UTFMax]byte
-	buf := make([]byte, 0, 3*len(s)/2) // Try to avoid more allocations.
+	return string(appendQuotedWith(make([]byte, 0, 3*len(s)/2), s, quote, ASCIIonly, graphicOnly))
+}
+
+func quoteRuneWith(r rune, quote byte, ASCIIonly, graphicOnly bool) string {
+	return string(appendQuotedRuneWith(nil, r, quote, ASCIIonly, graphicOnly))
+}
+
+func appendQuotedWith(buf []byte, s string, quote byte, ASCIIonly, graphicOnly bool) []byte {
 	buf = append(buf, quote)
 	for width := 0; len(s) > 0; s = s[width:] {
 		r := rune(s[0])
@@ -28,61 +32,76 @@ func quoteWith(s string, quote byte, ASCIIonly, graphicOnly bool) string {
 			buf = append(buf, lowerhex[s[0]&0xF])
 			continue
 		}
-		if r == rune(quote) || r == '\\' { // always backslashed
-			buf = append(buf, '\\')
+		buf = appendEscapedRune(buf, r, width, quote, ASCIIonly, graphicOnly)
+	}
+	buf = append(buf, quote)
+	return buf
+}
+
+func appendQuotedRuneWith(buf []byte, r rune, quote byte, ASCIIonly, graphicOnly bool) []byte {
+	buf = append(buf, quote)
+	if !utf8.ValidRune(r) {
+		r = utf8.RuneError
+	}
+	buf = appendEscapedRune(buf, r, utf8.RuneLen(r), quote, ASCIIonly, graphicOnly)
+	buf = append(buf, quote)
+	return buf
+}
+
+func appendEscapedRune(buf []byte, r rune, width int, quote byte, ASCIIonly, graphicOnly bool) []byte {
+	var runeTmp [utf8.UTFMax]byte
+	if r == rune(quote) || r == '\\' { // always backslashed
+		buf = append(buf, '\\')
+		buf = append(buf, byte(r))
+		return buf
+	}
+	if ASCIIonly {
+		if r < utf8.RuneSelf && IsPrint(r) {
 			buf = append(buf, byte(r))
-			continue
+			return buf
 		}
-		if ASCIIonly {
-			if r < utf8.RuneSelf && IsPrint(r) {
-				buf = append(buf, byte(r))
-				continue
+	} else if IsPrint(r) || graphicOnly && isInGraphicList(r) {
+		n := utf8.EncodeRune(runeTmp[:], r)
+		buf = append(buf, runeTmp[:n]...)
+		return buf
+	}
+	switch r {
+	case '\a':
+		buf = append(buf, `\a`...)
+	case '\b':
+		buf = append(buf, `\b`...)
+	case '\f':
+		buf = append(buf, `\f`...)
+	case '\n':
+		buf = append(buf, `\n`...)
+	case '\r':
+		buf = append(buf, `\r`...)
+	case '\t':
+		buf = append(buf, `\t`...)
+	case '\v':
+		buf = append(buf, `\v`...)
+	default:
+		switch {
+		case r < ' ':
+			buf = append(buf, `\x`...)
+			buf = append(buf, lowerhex[byte(r)>>4])
+			buf = append(buf, lowerhex[byte(r)&0xF])
+		case r > utf8.MaxRune:
+			r = 0xFFFD
+			fallthrough
+		case r < 0x10000:
+			buf = append(buf, `\u`...)
+			for s := 12; s >= 0; s -= 4 {
+				buf = append(buf, lowerhex[r>>uint(s)&0xF])
 			}
-		} else if IsPrint(r) || graphicOnly && isInGraphicList(r) {
-			n := utf8.EncodeRune(runeTmp[:], r)
-			buf = append(buf, runeTmp[:n]...)
-			continue
-		}
-		switch r {
-		case '\a':
-			buf = append(buf, `\a`...)
-		case '\b':
-			buf = append(buf, `\b`...)
-		case '\f':
-			buf = append(buf, `\f`...)
-		case '\n':
-			buf = append(buf, `\n`...)
-		case '\r':
-			buf = append(buf, `\r`...)
-		case '\t':
-			buf = append(buf, `\t`...)
-		case '\v':
-			buf = append(buf, `\v`...)
 		default:
-			switch {
-			case r < ' ':
-				buf = append(buf, `\x`...)
-				buf = append(buf, lowerhex[s[0]>>4])
-				buf = append(buf, lowerhex[s[0]&0xF])
-			case r > utf8.MaxRune:
-				r = 0xFFFD
-				fallthrough
-			case r < 0x10000:
-				buf = append(buf, `\u`...)
-				for s := 12; s >= 0; s -= 4 {
-					buf = append(buf, lowerhex[r>>uint(s)&0xF])
-				}
-			default:
-				buf = append(buf, `\U`...)
-				for s := 28; s >= 0; s -= 4 {
-					buf = append(buf, lowerhex[r>>uint(s)&0xF])
-				}
+			buf = append(buf, `\U`...)
+			for s := 28; s >= 0; s -= 4 {
+				buf = append(buf, lowerhex[r>>uint(s)&0xF])
 			}
 		}
 	}
-	buf = append(buf, quote)
-	return string(buf)
-
+	return buf
 }
 
 // Quote returns a double-quoted Go string literal representing s.  The
@@ -96,7 +115,7 @@ func Quote(s string) string {
 // AppendQuote appends a double-quoted Go string literal representing s,
 // as generated by Quote, to dst and returns the extended buffer.
 func AppendQuote(dst []byte, s string) []byte {
-	return append(dst, Quote(s)...)
+	return appendQuotedWith(dst, s, '"', false, false)
 }
 
 // QuoteToASCII returns a double-quoted Go string literal representing s.
@@ -109,7 +128,7 @@ func QuoteToASCII(s string) string {
 // AppendQuoteToASCII appends a double-quoted Go string literal representing s,
 // as generated by QuoteToASCII, to dst and returns the extended buffer.
 func AppendQuoteToASCII(dst []byte, s string) []byte {
-	return append(dst, QuoteToASCII(s)...)
+	return appendQuotedWith(dst, s, '"', true, false)
 }
 
 // QuoteToGraphic returns a double-quoted Go string literal representing s.
@@ -122,21 +141,20 @@ func QuoteToGraphic(s string) string {
 // AppendQuoteToGraphic appends a double-quoted Go string literal representing s,
 // as generated by QuoteToGraphic, to dst and returns the extended buffer.
 func AppendQuoteToGraphic(dst []byte, s string) []byte {
-	return append(dst, QuoteToGraphic(s)...)
+	return appendQuotedWith(dst, s, '"', false, true)
 }
 
 // QuoteRune returns a single-quoted Go character literal representing the
 // rune. The returned string uses Go escape sequences (\t, \n, \xFF, \u0100)
 // for control characters and non-printable characters as defined by IsPrint.
 func QuoteRune(r rune) string {
-	// TODO: avoid the allocation here.
-	return quoteWith(string(r), '\'', false, false)
+	return quoteRuneWith(r, '\'', false, false)
 }
 
 // AppendQuoteRune appends a single-quoted Go character literal representing the rune,
 // as generated by QuoteRune, to dst and returns the extended buffer.
 func AppendQuoteRune(dst []byte, r rune) []byte {
-	return append(dst, QuoteRune(r)...)
+	return appendQuotedRuneWith(dst, r, '\'', false, false)
 }
 
 // QuoteRuneToASCII returns a single-quoted Go character literal representing
@@ -144,14 +162,13 @@ func AppendQuoteRune(dst []byte, r rune) []byte {
 // \u0100) for non-ASCII characters and non-printable characters as defined
 // by IsPrint.
 func QuoteRuneToASCII(r rune) string {
-	// TODO: avoid the allocation here.
-	return quoteWith(string(r), '\'', true, false)
+	return quoteRuneWith(r, '\'', true, false)
 }
 
 // AppendQuoteRuneToASCII appends a single-quoted Go character literal representing the rune,
 // as generated by QuoteRuneToASCII, to dst and returns the extended buffer.
 func AppendQuoteRuneToASCII(dst []byte, r rune) []byte {
-	return append(dst, QuoteRuneToASCII(r)...)
+	return appendQuotedRuneWith(dst, r, '\'', true, false)
 }
 
 // QuoteRuneToGraphic returns a single-quoted Go character literal representing
@@ -159,14 +176,13 @@ func AppendQuoteRuneToASCII(dst []byte, r rune) []byte {
 // \u0100) for non-ASCII characters and non-printable characters as defined
 // by IsGraphic.
 func QuoteRuneToGraphic(r rune) string {
-	// TODO: avoid the allocation here.
-	return quoteWith(string(r), '\'', false, true)
+	return quoteRuneWith(r, '\'', false, true)
 }
 
 // AppendQuoteRuneToGraphic appends a single-quoted Go character literal representing the rune,
 // as generated by QuoteRuneToGraphic, to dst and returns the extended buffer.
 func AppendQuoteRuneToGraphic(dst []byte, r rune) []byte {
-	return append(dst, QuoteRuneToGraphic(r)...)
+	return appendQuotedRuneWith(dst, r, '\'', false, true)
 }
 
 // CanBackquote reports whether the string s can be represented
diff --git a/src/strconv/quote_test.go b/src/strconv/quote_test.go
index 3e8ec2c98f..10735e316c 100644
--- a/src/strconv/quote_test.go
+++ b/src/strconv/quote_test.go
@@ -89,6 +89,34 @@ func TestQuoteToGraphic(t *testing.T) {
 	}
 }
 
+func BenchmarkQuote(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		Quote("\a\b\f\r\n\t\v\a\b\f\r\n\t\v\a\b\f\r\n\t\v")
+	}
+}
+
+func BenchmarkQuoteRune(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		QuoteRune('\a')
+	}
+}
+
+var benchQuoteBuf []byte
+
+func BenchmarkAppendQuote(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		benchQuoteBuf = AppendQuote(benchQuoteBuf[:0], "\a\b\f\r\n\t\v\a\b\f\r\n\t\v\a\b\f\r\n\t\v")
+	}
+}
+
+var benchQuoteRuneBuf []byte
+
+func BenchmarkAppendQuoteRune(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		benchQuoteRuneBuf = AppendQuoteRune(benchQuoteRuneBuf[:0], '\a')
+	}
+}
+
 type quoteRuneTest struct {
 	in      rune
 	out     string