diff --git a/src/encoding/json/stream.go b/src/encoding/json/stream.go
index f6b62c4cf6..75a4270df7 100644
--- a/src/encoding/json/stream.go
+++ b/src/encoding/json/stream.go
@@ -12,12 +12,13 @@ import (
 
 // A Decoder reads and decodes JSON values from an input stream.
 type Decoder struct {
-	r     io.Reader
-	buf   []byte
-	d     decodeState
-	scanp int // start of unread data in buf
-	scan  scanner
-	err   error
+	r       io.Reader
+	buf     []byte
+	d       decodeState
+	scanp   int   // start of unread data in buf
+	scanned int64 // amount of data already scanned
+	scan    scanner
+	err     error
 
 	tokenState int
 	tokenStack []int
@@ -55,7 +56,7 @@ func (dec *Decoder) Decode(v interface{}) error {
 	}
 
 	if !dec.tokenValueAllowed() {
-		return &SyntaxError{msg: "not at beginning of value"}
+		return &SyntaxError{msg: "not at beginning of value", Offset: dec.offset()}
 	}
 
 	// Read whole value into buffer.
@@ -140,6 +141,7 @@ func (dec *Decoder) refill() error {
 	// Make room to read more into the buffer.
 	// First slide down data already consumed.
 	if dec.scanp > 0 {
+		dec.scanned += int64(dec.scanp)
 		n := copy(dec.buf, dec.buf[dec.scanp:])
 		dec.buf = dec.buf[:n]
 		dec.scanp = 0
@@ -306,7 +308,7 @@ func (dec *Decoder) tokenPrepareForDecode() error {
 			return err
 		}
 		if c != ',' {
-			return &SyntaxError{"expected comma after array element", 0}
+			return &SyntaxError{"expected comma after array element", dec.offset()}
 		}
 		dec.scanp++
 		dec.tokenState = tokenArrayValue
@@ -316,7 +318,7 @@ func (dec *Decoder) tokenPrepareForDecode() error {
 			return err
 		}
 		if c != ':' {
-			return &SyntaxError{"expected colon after object key", 0}
+			return &SyntaxError{"expected colon after object key", dec.offset()}
 		}
 		dec.scanp++
 		dec.tokenState = tokenObjectValue
@@ -433,7 +435,6 @@ func (dec *Decoder) Token() (Token, error) {
 				err := dec.Decode(&x)
 				dec.tokenState = old
 				if err != nil {
-					clearOffset(err)
 					return nil, err
 				}
 				dec.tokenState = tokenObjectColon
@@ -447,7 +448,6 @@ func (dec *Decoder) Token() (Token, error) {
 			}
 			var x interface{}
 			if err := dec.Decode(&x); err != nil {
-				clearOffset(err)
 				return nil, err
 			}
 			return x, nil
@@ -455,12 +455,6 @@ func (dec *Decoder) Token() (Token, error) {
 	}
 }
 
-func clearOffset(err error) {
-	if s, ok := err.(*SyntaxError); ok {
-		s.Offset = 0
-	}
-}
-
 func (dec *Decoder) tokenError(c byte) (Token, error) {
 	var context string
 	switch dec.tokenState {
@@ -477,7 +471,7 @@ func (dec *Decoder) tokenError(c byte) (Token, error) {
 	case tokenObjectComma:
 		context = " after object key:value pair"
 	}
-	return nil, &SyntaxError{"invalid character " + quoteChar(c) + " " + context, 0}
+	return nil, &SyntaxError{"invalid character " + quoteChar(c) + " " + context, dec.offset()}
 }
 
 // More reports whether there is another element in the
@@ -505,3 +499,7 @@ func (dec *Decoder) peek() (byte, error) {
 		err = dec.refill()
 	}
 }
+
+func (dec *Decoder) offset() int64 {
+	return dec.scanned + int64(dec.scanp)
+}
diff --git a/src/encoding/json/stream_test.go b/src/encoding/json/stream_test.go
index d0b3ffbce9..83c01d170c 100644
--- a/src/encoding/json/stream_test.go
+++ b/src/encoding/json/stream_test.go
@@ -342,11 +342,18 @@ var tokenStreamCases []tokenStreamCase = []tokenStreamCase{
 	{json: ` [{"a": 1} {"a": 2}] `, expTokens: []interface{}{
 		Delim('['),
 		decodeThis{map[string]interface{}{"a": float64(1)}},
-		decodeThis{&SyntaxError{"expected comma after array element", 0}},
+		decodeThis{&SyntaxError{"expected comma after array element", 11}},
 	}},
-	{json: `{ "a" 1 }`, expTokens: []interface{}{
-		Delim('{'), "a",
-		decodeThis{&SyntaxError{"expected colon after object key", 0}},
+	{json: `{ "` + strings.Repeat("a", 513) + `" 1 }`, expTokens: []interface{}{
+		Delim('{'), strings.Repeat("a", 513),
+		decodeThis{&SyntaxError{"expected colon after object key", 518}},
+	}},
+	{json: `{ "\a" }`, expTokens: []interface{}{
+		Delim('{'),
+		&SyntaxError{"invalid character 'a' in string escape code", 3},
+	}},
+	{json: ` \a`, expTokens: []interface{}{
+		&SyntaxError{"invalid character '\\\\' looking for beginning of value", 1},
 	}},
 }
 
@@ -367,15 +374,15 @@ func TestDecodeInStream(t *testing.T) {
 				tk, err = dec.Token()
 			}
 			if experr, ok := etk.(error); ok {
-				if err == nil || err.Error() != experr.Error() {
-					t.Errorf("case %v: Expected error %v in %q, but was %v", ci, experr, tcase.json, err)
+				if err == nil || !reflect.DeepEqual(err, experr) {
+					t.Errorf("case %v: Expected error %#v in %q, but was %#v", ci, experr, tcase.json, err)
 				}
 				break
 			} else if err == io.EOF {
 				t.Errorf("case %v: Unexpected EOF in %q", ci, tcase.json)
 				break
 			} else if err != nil {
-				t.Errorf("case %v: Unexpected error '%v' in %q", ci, err, tcase.json)
+				t.Errorf("case %v: Unexpected error '%#v' in %q", ci, err, tcase.json)
 				break
 			}
 			if !reflect.DeepEqual(tk, etk) {