diff --git a/go/operation/upload_content.go b/go/operation/upload_content.go
index 27ebb0f5a..cae657b2c 100644
--- a/go/operation/upload_content.go
+++ b/go/operation/upload_content.go
@@ -4,12 +4,10 @@ import (
 	"bytes"
 	"encoding/json"
 	"errors"
-	"path/filepath"
 	_ "fmt"
 	"io"
 	"io/ioutil"
 	"log"
-	"mime"
 	"mime/multipart"
 	"net/http"
 )
@@ -31,8 +29,7 @@ func Upload(uploadUrl string, filename string, reader io.Reader) (*UploadResult,
 		log.Println("error copying data", err)
 		return nil, err
 	}
-	content_type := mime.TypeByExtension(filepath.Ext(filename))
-  content_type := body_writer.FormDataContentType()
+	content_type := body_writer.FormDataContentType()
 	if err = body_writer.Close(); err != nil {
 		log.Println("error closing body", err)
 		return nil, err