diff --git a/mercurial/extensions.py b/mercurial/extensions.py
--- a/mercurial/extensions.py
+++ b/mercurial/extensions.py
@@ -349,12 +349,13 @@ def disabledcmd(ui, cmd, strict=False):
 
     raise error.UnknownCommand(cmd)
 
-def enabled():
+def enabled(shortname=True):
     '''return a dict of {name: desc} of extensions'''
     exts = {}
     for ename, ext in extensions():
         doc = (gettext(ext.__doc__) or _('(no help text available)'))
-        ename = ename.split('.')[-1]
+        if shortname:
+            ename = ename.split('.')[-1]
         exts[ename] = doc.splitlines()[0].strip()
 
     return exts
diff --git a/mercurial/help.py b/mercurial/help.py
--- a/mercurial/help.py
+++ b/mercurial/help.py
@@ -103,10 +103,11 @@ def topicmatch(kw):
             cmdname = cmd.split('|')[0].lstrip('^')
             results['commands'].append((cmdname, summary))
     for name, docs in itertools.chain(
-        extensions.enabled().iteritems(),
+        extensions.enabled(False).iteritems(),
         extensions.disabled().iteritems()):
         # extensions.load ignores the UI argument
         mod = extensions.load(None, name, '')
+        name = name.split('.')[-1]
         if lowercontains(name) or lowercontains(docs):
             # extension docs are already translated
             results['extensions'].append((name, docs.splitlines()[0]))
diff --git a/tests/test-help.t b/tests/test-help.t
--- a/tests/test-help.t
+++ b/tests/test-help.t
@@ -773,6 +773,12 @@ Test help hooks
 
 Test keyword search help
 
+  $ cat > prefixedname.py <<EOF
+  > '''matched against word "clone"
+  > '''
+  > EOF
+  $ echo '[extensions]' >> $HGRCPATH
+  $ echo "dot.dot.prefixedname = `pwd`/prefixedname.py" >> $HGRCPATH
   $ hg help -k clone
   Topics:
   
@@ -792,7 +798,8 @@ Test keyword search help
   
   Extensions:
   
-   relink recreates hardlinks between repository clones
+   prefixedname matched against word "clone"
+   relink       recreates hardlinks between repository clones
   
   Extension Commands: