diff --git a/src/net/http/request.go b/src/net/http/request.go
index 26da7adc25..1eb6d39067 100644
--- a/src/net/http/request.go
+++ b/src/net/http/request.go
@@ -431,7 +431,7 @@ func (r *Request) multipartReader(allowMixed bool) (*multipart.Reader, error) {
 		return nil, ErrNotMultipart
 	}
 	d, params, err := mime.ParseMediaType(v)
-	if err != nil || d != "multipart/form-data" || (allowMixed && d != "multipart/mixed") {
+	if err != nil || !(d == "multipart/form-data" || allowMixed && d == "multipart/mixed") {
 		return nil, ErrNotMultipart
 	}
 	boundary, ok := params["boundary"]
diff --git a/src/net/http/request_test.go b/src/net/http/request_test.go
index fa716ee59d..aaf9d5cb9b 100644
--- a/src/net/http/request_test.go
+++ b/src/net/http/request_test.go
@@ -143,6 +143,16 @@ func TestMultipartReader(t *testing.T) {
 		t.Errorf("expected multipart; error: %v", err)
 	}
 
+	req = &Request{
+		Method: "POST",
+		Header: Header{"Content-Type": {`multipart/mixed; boundary="foo123"`}},
+		Body:   ioutil.NopCloser(new(bytes.Buffer)),
+	}
+	multipart, err = req.MultipartReader()
+	if multipart == nil {
+		t.Errorf("expected multipart; error: %v", err)
+	}
+
 	req.Header = Header{"Content-Type": {"text/plain"}}
 	multipart, err = req.MultipartReader()
 	if multipart != nil {