diff --git a/src/net/http/serve_test.go b/src/net/http/serve_test.go
index 0c76f1bcc4e44..21858694144ce 100644
--- a/src/net/http/serve_test.go
+++ b/src/net/http/serve_test.go
@@ -4799,6 +4799,10 @@ func TestServerValidatesHeaders(t *testing.T) {
 		{"Foo : bar\r\n", 400},
 		{"Foo\t: bar\r\n", 400},
 
+		// Empty header keys are invalid.
+		// See RFC 7230, Section 3.2.
+		{": empty key\r\n", 400},
+
 		{"foo: foo foo\r\n", 200},    // LWS space is okay
 		{"foo: foo\tfoo\r\n", 200},   // LWS tab is okay
 		{"foo: foo\x00foo\r\n", 400}, // CTL 0x00 in value is bad
diff --git a/src/net/textproto/reader.go b/src/net/textproto/reader.go
index a603564fb8b06..ee7eb0200bf4e 100644
--- a/src/net/textproto/reader.go
+++ b/src/net/textproto/reader.go
@@ -535,13 +535,6 @@ func readMIMEHeader(r *Reader, maxMemory, maxHeaders int64) (MIMEHeader, error)
 			}
 		}
 
-		// As per RFC 7230 field-name is a token, tokens consist of one or more chars.
-		// We could return a ProtocolError here, but better to be liberal in what we
-		// accept, so if we get an empty key, skip it.
-		if key == "" {
-			continue
-		}
-
 		maxHeaders--
 		if maxHeaders < 0 {
 			return nil, errors.New("message too large")
@@ -725,6 +718,10 @@ func validHeaderValueByte(c byte) bool {
 // ReadMIMEHeader accepts header keys containing spaces, but does not
 // canonicalize them.
 func canonicalMIMEHeaderKey(a []byte) (_ string, ok bool) {
+	if len(a) == 0 {
+		return "", false
+	}
+
 	// See if a looks like a header key. If not, return it unchanged.
 	noCanon := false
 	for _, c := range a {
diff --git a/src/net/textproto/reader_test.go b/src/net/textproto/reader_test.go
index 696ae406f3860..c9c0a98ea4452 100644
--- a/src/net/textproto/reader_test.go
+++ b/src/net/textproto/reader_test.go
@@ -169,8 +169,8 @@ func TestReaderUpcomingHeaderKeys(t *testing.T) {
 func TestReadMIMEHeaderNoKey(t *testing.T) {
 	r := reader(": bar\ntest-1: 1\n\n")
 	m, err := r.ReadMIMEHeader()
-	want := MIMEHeader{"Test-1": {"1"}}
-	if !reflect.DeepEqual(m, want) || err != nil {
+	want := MIMEHeader{}
+	if !reflect.DeepEqual(m, want) || err == nil {
 		t.Fatalf("ReadMIMEHeader: %v, %v; want %v", m, err, want)
 	}
 }
@@ -227,6 +227,7 @@ func TestReadMIMEHeaderMalformed(t *testing.T) {
 		"Foo\r\n\t: foo\r\n\r\n",
 		"Foo-\n\tBar",
 		"Foo \tBar: foo\r\n\r\n",
+		": empty key\r\n\r\n",
 	}
 	for _, input := range inputs {
 		r := reader(input)