diff --git a/mercurial/streamclone.py b/mercurial/streamclone.py
--- a/mercurial/streamclone.py
+++ b/mercurial/streamclone.py
@@ -17,6 +17,10 @@ from . import (
     util,
 )
 
+def allowservergeneration(ui):
+    """Whether streaming clones are allowed from the server."""
+    return ui.configbool('server', 'uncompressed', True, untrusted=True)
+
 # This is it's own function so extensions can override it.
 def _walkstreamfiles(repo):
     return repo.store.walk()
diff --git a/mercurial/wireproto.py b/mercurial/wireproto.py
--- a/mercurial/wireproto.py
+++ b/mercurial/wireproto.py
@@ -564,7 +564,7 @@ def _capabilities(repo, proto):
     """
     # copy to prevent modification of the global list
     caps = list(wireprotocaps)
-    if _allowstream(repo.ui):
+    if streamclone.allowservergeneration(repo.ui):
         if repo.ui.configbool('server', 'preferuncompressed', False):
             caps.append('stream-preferred')
         requiredformats = repo.requirements & repo.supportedformats
@@ -701,16 +701,13 @@ def pushkey(repo, proto, namespace, key,
                      encoding.tolocal(old), new)
     return '%s\n' % int(r)
 
-def _allowstream(ui):
-    return ui.configbool('server', 'uncompressed', True, untrusted=True)
-
 @wireprotocommand('stream_out')
 def stream(repo, proto):
     '''If the server supports streaming clone, it advertises the "stream"
     capability with a value representing the version and flags of the repo
     it is serving. Client checks to see if it understands the format.
     '''
-    if not _allowstream(repo.ui):
+    if not streamclone.allowservergeneration(repo.ui):
         return '1\n'
 
     def getstream(it):