diff --git a/src/pkg/encoding/json/decode.go b/src/pkg/encoding/json/decode.go
index 458fb39ec0..4db566726e 100644
--- a/src/pkg/encoding/json/decode.go
+++ b/src/pkg/encoding/json/decode.go
@@ -8,6 +8,7 @@
 package json
 
 import (
+	"bytes"
 	"encoding"
 	"encoding/base64"
 	"errors"
@@ -15,7 +16,6 @@ import (
 	"reflect"
 	"runtime"
 	"strconv"
-	"strings"
 	"unicode"
 	"unicode/utf16"
 	"unicode/utf8"
@@ -500,11 +500,11 @@ func (d *decodeState) object(v reflect.Value) {
 			d.error(errPhase)
 		}
 
-		// Read string key.
+		// Read key.
 		start := d.off - 1
 		op = d.scanWhile(scanContinue)
 		item := d.data[start : d.off-1]
-		key, ok := unquote(item)
+		key, ok := unquoteBytes(item)
 		if !ok {
 			d.error(errPhase)
 		}
@@ -526,11 +526,11 @@ func (d *decodeState) object(v reflect.Value) {
 			fields := cachedTypeFields(v.Type())
 			for i := range fields {
 				ff := &fields[i]
-				if ff.name == key {
+				if bytes.Equal(ff.nameBytes, key) {
 					f = ff
 					break
 				}
-				if f == nil && strings.EqualFold(ff.name, key) {
+				if f == nil && ff.equalFold(ff.nameBytes, key) {
 					f = ff
 				}
 			}
diff --git a/src/pkg/encoding/json/encode.go b/src/pkg/encoding/json/encode.go
index 7d6c71d7a9..8c71770ca4 100644
--- a/src/pkg/encoding/json/encode.go
+++ b/src/pkg/encoding/json/encode.go
@@ -936,6 +936,9 @@ func (e *encodeState) stringBytes(s []byte) (int, error) {
 // A field represents a single field found in a struct.
 type field struct {
 	name      string
+	nameBytes []byte                 // []byte(name)
+	equalFold func(s, t []byte) bool // bytes.EqualFold or equivalent
+
 	tag       bool
 	index     []int
 	typ       reflect.Type
@@ -943,6 +946,12 @@ type field struct {
 	quoted    bool
 }
 
+func fillField(f field) field {
+	f.nameBytes = []byte(f.name)
+	f.equalFold = foldFunc(f.nameBytes)
+	return f
+}
+
 // byName sorts field by name, breaking ties with depth,
 // then breaking ties with "name came from json tag", then
 // breaking ties with index sequence.
@@ -1042,8 +1051,14 @@ func typeFields(t reflect.Type) []field {
 					if name == "" {
 						name = sf.Name
 					}
-					fields = append(fields, field{name, tagged, index, ft,
-						opts.Contains("omitempty"), opts.Contains("string")})
+					fields = append(fields, fillField(field{
+						name:      name,
+						tag:       tagged,
+						index:     index,
+						typ:       ft,
+						omitEmpty: opts.Contains("omitempty"),
+						quoted:    opts.Contains("string"),
+					}))
 					if count[f.typ] > 1 {
 						// If there were multiple instances, add a second,
 						// so that the annihilation code will see a duplicate.
@@ -1057,7 +1072,7 @@ func typeFields(t reflect.Type) []field {
 				// Record new anonymous struct to explore in next round.
 				nextCount[ft]++
 				if nextCount[ft] == 1 {
-					next = append(next, field{name: ft.Name(), index: index, typ: ft})
+					next = append(next, fillField(field{name: ft.Name(), index: index, typ: ft}))
 				}
 			}
 		}
diff --git a/src/pkg/encoding/json/fold.go b/src/pkg/encoding/json/fold.go
new file mode 100644
index 0000000000..d6f77c93e5
--- /dev/null
+++ b/src/pkg/encoding/json/fold.go
@@ -0,0 +1,143 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package json
+
+import (
+	"bytes"
+	"unicode/utf8"
+)
+
+const (
+	caseMask     = ^byte(0x20) // Mask to ignore case in ASCII.
+	kelvin       = '\u212a'
+	smallLongEss = '\u017f'
+)
+
+// foldFunc returns one of four different case folding equivalence
+// functions, from most general (and slow) to fastest:
+//
+// 1) bytes.EqualFold, if the key s contains any non-ASCII UTF-8
+// 2) equalFoldRight, if s contains special folding ASCII ('k', 'K', 's', 'S')
+// 3) asciiEqualFold, no special, but includes non-letters (including _)
+// 4) simpleLetterEqualFold, no specials, no non-letters.
+//
+// The letters S and K are special because they map to 3 runes, not just 2:
+//  * S maps to s and to U+017F 'ſ' Latin small letter long s
+//  * k maps to K and to U+212A 'K' Kelvin sign
+// See http://play.golang.org/p/tTxjOc0OGo
+//
+// The returned function is specialized for matching against s and
+// should only be given s. It's not curried for performance reasons.
+func foldFunc(s []byte) func(s, t []byte) bool {
+	nonLetter := false
+	special := false // special letter
+	for _, b := range s {
+		if b >= utf8.RuneSelf {
+			return bytes.EqualFold
+		}
+		upper := b & caseMask
+		if upper < 'A' || upper > 'Z' {
+			nonLetter = true
+		} else if upper == 'K' || upper == 'S' {
+			// See above for why these letters are special.
+			special = true
+		}
+	}
+	if special {
+		return equalFoldRight
+	}
+	if nonLetter {
+		return asciiEqualFold
+	}
+	return simpleLetterEqualFold
+}
+
+// equalFoldRight is a specialization of bytes.EqualFold when s is
+// known to be all ASCII (including punctuation), but contains an 's',
+// 'S', 'k', or 'K', requiring a Unicode fold on the bytes in t.
+// See comments on foldFunc.
+func equalFoldRight(s, t []byte) bool {
+	for _, sb := range s {
+		if len(t) == 0 {
+			return false
+		}
+		tb := t[0]
+		if tb < utf8.RuneSelf {
+			if sb != tb {
+				sbUpper := sb & caseMask
+				if 'A' <= sbUpper && sbUpper <= 'Z' {
+					if sbUpper != tb&caseMask {
+						return false
+					}
+				} else {
+					return false
+				}
+			}
+			t = t[1:]
+			continue
+		}
+		// sb is ASCII and t is not. t must be either kelvin
+		// sign or long s; sb must be s, S, k, or K.
+		tr, size := utf8.DecodeRune(t)
+		switch sb {
+		case 's', 'S':
+			if tr != smallLongEss {
+				return false
+			}
+		case 'k', 'K':
+			if tr != kelvin {
+				return false
+			}
+		default:
+			return false
+		}
+		t = t[size:]
+
+	}
+	if len(t) > 0 {
+		return false
+	}
+	return true
+}
+
+// asciiEqualFold is a specialization of bytes.EqualFold for use when
+// s is all ASCII (but may contain non-letters) and contains no
+// special-folding letters.
+// See comments on foldFunc.
+func asciiEqualFold(s, t []byte) bool {
+	if len(s) != len(t) {
+		return false
+	}
+	for i, sb := range s {
+		tb := t[i]
+		if sb == tb {
+			continue
+		}
+		if ('a' <= sb && sb <= 'z') || ('A' <= sb && sb <= 'Z') {
+			if sb&caseMask != tb&caseMask {
+				return false
+			}
+		} else {
+			return false
+		}
+	}
+	return true
+}
+
+// simpleLetterEqualFold is a specialization of bytes.EqualFold for
+// use when s is all ASCII letters (no underscores, etc) and also
+// doesn't contain 'k', 'K', 's', or 'S'.
+// See comments on foldFunc.
+func simpleLetterEqualFold(s, t []byte) bool {
+	if len(s) != len(t) {
+		return false
+	}
+	for i, b := range s {
+		if b&caseMask != t[i]&caseMask {
+			return false
+		}
+	}
+	return true
+}
diff --git a/src/pkg/encoding/json/fold_test.go b/src/pkg/encoding/json/fold_test.go
new file mode 100644
index 0000000000..9fb94646a8
--- /dev/null
+++ b/src/pkg/encoding/json/fold_test.go
@@ -0,0 +1,116 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package json
+
+import (
+	"bytes"
+	"strings"
+	"testing"
+	"unicode/utf8"
+)
+
+var foldTests = []struct {
+	fn   func(s, t []byte) bool
+	s, t string
+	want bool
+}{
+	{equalFoldRight, "", "", true},
+	{equalFoldRight, "a", "a", true},
+	{equalFoldRight, "", "a", false},
+	{equalFoldRight, "a", "", false},
+	{equalFoldRight, "a", "A", true},
+	{equalFoldRight, "AB", "ab", true},
+	{equalFoldRight, "AB", "ac", false},
+	{equalFoldRight, "sbkKc", "ſbKKc", true},
+	{equalFoldRight, "SbKkc", "ſbKKc", true},
+	{equalFoldRight, "SbKkc", "ſbKK", false},
+	{equalFoldRight, "e", "é", false},
+	{equalFoldRight, "s", "S", true},
+
+	{simpleLetterEqualFold, "", "", true},
+	{simpleLetterEqualFold, "abc", "abc", true},
+	{simpleLetterEqualFold, "abc", "ABC", true},
+	{simpleLetterEqualFold, "abc", "ABCD", false},
+	{simpleLetterEqualFold, "abc", "xxx", false},
+
+	{asciiEqualFold, "a_B", "A_b", true},
+	{asciiEqualFold, "aa@", "aa`", false}, // verify 0x40 and 0x60 aren't case-equivalent
+}
+
+func TestFold(t *testing.T) {
+	for i, tt := range foldTests {
+		if got := tt.fn([]byte(tt.s), []byte(tt.t)); got != tt.want {
+			t.Errorf("%d. %q, %q = %v; want %v", i, tt.s, tt.t, got, tt.want)
+		}
+		truth := strings.EqualFold(tt.s, tt.t)
+		if truth != tt.want {
+			t.Errorf("strings.EqualFold doesn't agree with case %d", i)
+		}
+	}
+}
+
+func TestFoldAgainstUnicode(t *testing.T) {
+	const bufSize = 5
+	buf1 := make([]byte, 0, bufSize)
+	buf2 := make([]byte, 0, bufSize)
+	var runes []rune
+	for i := 0x20; i <= 0x7f; i++ {
+		runes = append(runes, rune(i))
+	}
+	runes = append(runes, kelvin, smallLongEss)
+
+	funcs := []struct {
+		name   string
+		fold   func(s, t []byte) bool
+		letter bool // must be ASCII letter
+		simple bool // must be simple ASCII letter (not 'S' or 'K')
+	}{
+		{
+			name: "equalFoldRight",
+			fold: equalFoldRight,
+		},
+		{
+			name:   "asciiEqualFold",
+			fold:   asciiEqualFold,
+			simple: true,
+		},
+		{
+			name:   "simpleLetterEqualFold",
+			fold:   simpleLetterEqualFold,
+			simple: true,
+			letter: true,
+		},
+	}
+
+	for _, ff := range funcs {
+		for _, r := range runes {
+			if r >= utf8.RuneSelf {
+				continue
+			}
+			if ff.letter && !isASCIILetter(byte(r)) {
+				continue
+			}
+			if ff.simple && (r == 's' || r == 'S' || r == 'k' || r == 'K') {
+				continue
+			}
+			for _, r2 := range runes {
+				buf1 := append(buf1[:0], 'x')
+				buf2 := append(buf2[:0], 'x')
+				buf1 = buf1[:1+utf8.EncodeRune(buf1[1:bufSize], r)]
+				buf2 = buf2[:1+utf8.EncodeRune(buf2[1:bufSize], r2)]
+				buf1 = append(buf1, 'x')
+				buf2 = append(buf2, 'x')
+				want := bytes.EqualFold(buf1, buf2)
+				if got := ff.fold(buf1, buf2); got != want {
+					t.Errorf("%s(%q, %q) = %v; want %v", ff.name, buf1, buf2, got, want)
+				}
+			}
+		}
+	}
+}
+
+func isASCIILetter(b byte) bool {
+	return ('A' <= b && b <= 'Z') || ('a' <= b && b <= 'z')
+}