diff --git a/mercurial/hgweb/request.py b/mercurial/hgweb/request.py
--- a/mercurial/hgweb/request.py
+++ b/mercurial/hgweb/request.py
@@ -200,6 +200,13 @@
 
     headers = wsgiheaders.Headers(headers)
 
+    # This is kind of a lie because the HTTP header wasn't explicitly
+    # sent. But for all intents and purposes it should be OK to lie about
+    # this, since a consumer will either either value to determine how many
+    # bytes are available to read.
+    if 'CONTENT_LENGTH' in env and 'HTTP_CONTENT_LENGTH' not in env:
+        headers['Content-Length'] = env['CONTENT_LENGTH']
+
     return parsedrequest(url=fullurl, baseurl=baseurl,
                          advertisedurl=advertisedfullurl,
                          advertisedbaseurl=advertisedbaseurl,
diff --git a/mercurial/wireprotoserver.py b/mercurial/wireprotoserver.py
--- a/mercurial/wireprotoserver.py
+++ b/mercurial/wireprotoserver.py
@@ -91,10 +91,9 @@
         return args
 
     def forwardpayload(self, fp):
-        if b'Content-Length' in self._req.headers:
-            length = int(self._req.headers[b'Content-Length'])
-        else:
-            length = int(self._wsgireq.env[r'CONTENT_LENGTH'])
+        # TODO Content-Length may not always be defined.
+        length = int(self._req.headers[b'Content-Length'])
+
         # If httppostargs is used, we need to read Content-Length
         # minus the amount that was consumed by args.
         length -= int(self._req.headers.get(b'X-HgArgs-Post', 0))