diff --git a/mercurial/dispatch.py b/mercurial/dispatch.py
--- a/mercurial/dispatch.py
+++ b/mercurial/dispatch.py
@@ -766,7 +766,7 @@ def _dispatch(req):
     if options['version']:
         return commands.version_(ui)
     if options['help']:
-        return commands.help_(ui, cmd)
+        return commands.help_(ui, cmd, command=True)
     elif not cmd:
         return commands.help_(ui, 'shortlist')
 
diff --git a/tests/test-help.t b/tests/test-help.t
--- a/tests/test-help.t
+++ b/tests/test-help.t
@@ -862,6 +862,17 @@ test deprecated option is hidden with tr
   *"hg -v help debugoptDEP"* (glob)
 #endif
 
+Test commands that collide with topics (issue4240)
+
+  $ hg config -hq
+  hg config [-u] [NAME]...
+  
+  show combined config settings from all hgrc files
+  $ hg showconfig -hq
+  hg config [-u] [NAME]...
+  
+  show combined config settings from all hgrc files
+
 Test a help topic
 
   $ hg help revs