diff --git a/src/encoding/csv/reader.go b/src/encoding/csv/reader.go
index 00b9bbffee..031ee6cedb 100644
--- a/src/encoding/csv/reader.go
+++ b/src/encoding/csv/reader.go
@@ -88,6 +88,12 @@ var (
 	ErrFieldCount    = errors.New("wrong number of fields")
 )
 
+var errInvalidDelim = errors.New("csv: invalid field or comment delimiter")
+
+func validDelim(r rune) bool {
+	return r != 0 && r != '\r' && r != '\n' && utf8.ValidRune(r) && r != utf8.RuneError
+}
+
 // A Reader reads records from a CSV-encoded file.
 //
 // As returned by NewReader, a Reader expects input conforming to RFC 4180.
@@ -232,6 +238,10 @@ func nextRune(b []byte) rune {
 }
 
 func (r *Reader) readRecord(dst []string) ([]string, error) {
+	if r.Comma == r.Comment || !validDelim(r.Comma) || (r.Comment != 0 && !validDelim(r.Comment)) {
+		return nil, errInvalidDelim
+	}
+
 	// Read line (automatically skipping past empty lines and any comments).
 	var line, fullLine []byte
 	var errRead error
diff --git a/src/encoding/csv/reader_test.go b/src/encoding/csv/reader_test.go
index ed7d89dfe0..48efbb6719 100644
--- a/src/encoding/csv/reader_test.go
+++ b/src/encoding/csv/reader_test.go
@@ -9,6 +9,7 @@ import (
 	"reflect"
 	"strings"
 	"testing"
+	"unicode/utf8"
 )
 
 func TestRead(t *testing.T) {
@@ -312,6 +313,35 @@ x,,,
 		Input:      `"""""""`,
 		Output:     [][]string{{`"""`}},
 		LazyQuotes: true,
+	}, {
+		Name:  "BadComma1",
+		Comma: '\n',
+		Error: errInvalidDelim,
+	}, {
+		Name:  "BadComma2",
+		Comma: '\r',
+		Error: errInvalidDelim,
+	}, {
+		Name:  "BadComma3",
+		Comma: utf8.RuneError,
+		Error: errInvalidDelim,
+	}, {
+		Name:    "BadComment1",
+		Comment: '\n',
+		Error:   errInvalidDelim,
+	}, {
+		Name:    "BadComment2",
+		Comment: '\r',
+		Error:   errInvalidDelim,
+	}, {
+		Name:    "BadComment3",
+		Comment: utf8.RuneError,
+		Error:   errInvalidDelim,
+	}, {
+		Name:    "BadCommaComment",
+		Comma:   'X',
+		Comment: 'X',
+		Error:   errInvalidDelim,
 	}}
 
 	for _, tt := range tests {
diff --git a/src/encoding/csv/writer.go b/src/encoding/csv/writer.go
index 84b7aa1ed1..b23cae4517 100644
--- a/src/encoding/csv/writer.go
+++ b/src/encoding/csv/writer.go
@@ -38,6 +38,10 @@ func NewWriter(w io.Writer) *Writer {
 // Writer writes a single CSV record to w along with any necessary quoting.
 // A record is a slice of strings with each string being one field.
 func (w *Writer) Write(record []string) error {
+	if !validDelim(w.Comma) {
+		return errInvalidDelim
+	}
+
 	for n, field := range record {
 		if n > 0 {
 			if _, err := w.w.WriteRune(w.Comma); err != nil {