diff --git a/mercurial/dispatch.py b/mercurial/dispatch.py
--- a/mercurial/dispatch.py
+++ b/mercurial/dispatch.py
@@ -635,8 +635,7 @@ def _checkshellalias(lui, ui, args):
 
     cmd = args[0]
     try:
-        aliases, entry = cmdutil.findcmd(cmd, cmdtable,
-                                         lui.configbool("ui", "strict"))
+        aliases, entry = cmdutil.findcmd(cmd, cmdtable)
     except (error.AmbiguousCommand, error.UnknownCommand):
         restorecommands()
         return
diff --git a/tests/test-alias.t b/tests/test-alias.t
--- a/tests/test-alias.t
+++ b/tests/test-alias.t
@@ -324,6 +324,21 @@ shell aliases with escaped $ chars
   $ hg escaped4 test
   $0 $@
 
+abbreviated name, which matches against both shell alias and the
+command provided extension, should be aborted.
+
+  $ cat >> .hg/hgrc <<EOF
+  > [extensions]
+  > hgext.rebase =
+  > [alias]
+  > rebate = !echo this is rebate
+  > EOF
+  $ hg reba
+  hg: command 'reba' is ambiguous:
+      rebase rebate
+  [255]
+  $ hg rebat
+  this is rebate
 
 invalid arguments