--- a/mercurial/__init__.py	Sun May 28 17:02:24 2017 -0400
+++ b/mercurial/__init__.py	Sun May 28 15:45:47 2017 -0400
@@ -34,6 +34,9 @@
             # zstd is already dual-version clean, don't try and mangle it
             if fullname.startswith('mercurial.zstd'):
                 return None
+            # pywatchman is already dual-version clean, don't try and mangle it
+            if fullname.startswith('hgext.fsmonitor.pywatchman'):
+                return None
 
             # Try to find the module using other registered finders.
             spec = None