diff --git a/coreapi/transports/http.py b/coreapi/transports/http.py
index ecd5bb0..d586021 100644
--- a/coreapi/transports/http.py
+++ b/coreapi/transports/http.py
@@ -12,6 +12,16 @@
 import mimetypes
 import uritemplate
 import warnings
+from requests_toolbelt.multipart.encoder import MultipartEncoder, MultipartEncoderMonitor
+import tqdm
+
+def tqdm_callback(encoder):
+    bar = tqdm.tqdm(total=encoder.len, unit="b")
+
+    def callback(monitor):
+        bar.update(monitor.bytes_read - bar.n)
+
+    return callback
 
 
 Params = collections.namedtuple('Params', ['path', 'query', 'data', 'files'])
@@ -222,8 +232,19 @@ def _build_http_request(session, url, method, headers=None, encoding=None, param
         if encoding == 'application/json':
             opts['json'] = params.data
         elif encoding == 'multipart/form-data':
-            opts['data'] = params.data
-            opts['files'] = ForceMultiPartDict(params.files)
+            send_data = []
+            for k,v in params.data.items():
+                if isinstance(v, (list, tuple)):
+                    for item in v:
+                        send_data.append((k,item))
+                else:
+                    send_data.append((k,v))
+            for k,v in params.files.items():
+                send_data.append((k, (guess_filename(v) or k, v, 'application/*')))
+            e = MultipartEncoder(send_data)
+            monitor = MultipartEncoderMonitor(e, callback=tqdm_callback(e))
+            opts['data'] = monitor
+            opts['headers'].update({'Content-Type': monitor.content_type})
         elif encoding == 'application/x-www-form-urlencoded':
             opts['data'] = params.data
         elif encoding == 'application/octet-stream':
diff --git a/requirements.txt b/requirements.txt
index 77e66d0..f47d6c8 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -4,6 +4,7 @@ itypes
 requests
 uritemplate
 tqdm
+requests-toolbelt
 
 # Testing requirements
 coverage
diff --git a/setup.py b/setup.py
index 39f0aa3..9966431 100755
--- a/setup.py
+++ b/setup.py
@@ -67,7 +67,8 @@ def get_package_data(package):
         'requests',
         'itypes',
         'uritemplate',
-        'tqdm'
+        'tqdm',
+        'requests-toolbelt'
     ],
     entry_points={
         'coreapi.codecs': [