diff --git a/mitmproxy/web/app.py b/mitmproxy/web/app.py
index c2d46d303..b130a6f71 100644
--- a/mitmproxy/web/app.py
+++ b/mitmproxy/web/app.py
@@ -297,12 +297,9 @@ class FlowContent(RequestHandler):
 
         flow = self.flow
         flow.backup()
-        content = ''
+        content = 'Can not read file!'
         if (len(self.request.files.values()) > 0):
             content = self.request.files.values()[0][0]["body"]
-        elif (len(self.request.arguments) > 0):
-            content = self.request.arguments['file']
-
         flow.response.content = str(content)
         self.state.update_flow(flow)
 
diff --git a/web/src/js/ducks/flows.js b/web/src/js/ducks/flows.js
index 36274f398..8815db255 100644
--- a/web/src/js/ducks/flows.js
+++ b/web/src/js/ducks/flows.js
@@ -119,6 +119,8 @@ export function update(flow, data) {
 
 export function update_content(flow, file) {
     const body = new FormData()
+    if (typeof file !== File)
+        file = new Blob([file], {type: 'plain/text'})
     body.append('file', file)
     fetchApi(`/flows/${flow.id}/response/content`, {method: 'post',  body} )
     return { type: REQUEST_ACTION }