diff --git a/tests/test-releasenotes-formatting.t b/tests/test-releasenotes-formatting.t
--- a/tests/test-releasenotes-formatting.t
+++ b/tests/test-releasenotes-formatting.t
@@ -434,3 +434,43 @@
   $ hg releasenotes -l -c
   abort: cannot use both '--list' and '--check'
   [255]
+
+Raise error when no filename is specified with --rev
+
+  $ hg init relnotes-nofile
+  $ cd relnotes-nofile
+  $ hg releasenote -r .
+  ** unknown exception encountered, please report by visiting
+  ** https://mercurial-scm.org/wiki/BugTracker
+  ** Python 2.7.12 (default, Nov 19 2016, 06:48:10) [GCC 5.4.0 20160609]
+  ** Mercurial Distributed SCM (version 4.3.3+701-c4594d38b2da+20171001)
+  ** Extensions loaded: releasenotes
+  Traceback (most recent call last):
+    File "/tmp/hgtests.5N93rp/install/bin/hg", line 47, in <module>
+      dispatch.run()
+    File "/tmp/hgtests.5N93rp/install/lib/python/mercurial/dispatch.py", line 81, in run
+      status = (dispatch(req) or 0) & 255
+    File "/tmp/hgtests.5N93rp/install/lib/python/mercurial/dispatch.py", line 163, in dispatch
+      ret = _runcatch(req)
+    File "/tmp/hgtests.5N93rp/install/lib/python/mercurial/dispatch.py", line 303, in _runcatch
+      return _callcatch(ui, _runcatchfunc)
+    File "/tmp/hgtests.5N93rp/install/lib/python/mercurial/dispatch.py", line 311, in _callcatch
+      return scmutil.callcatch(ui, func)
+    File "/tmp/hgtests.5N93rp/install/lib/python/mercurial/scmutil.py", line 151, in callcatch
+      return func()
+    File "/tmp/hgtests.5N93rp/install/lib/python/mercurial/dispatch.py", line 293, in _runcatchfunc
+      return _dispatch(req)
+    File "/tmp/hgtests.5N93rp/install/lib/python/mercurial/dispatch.py", line 929, in _dispatch
+      cmdpats, cmdoptions)
+    File "/tmp/hgtests.5N93rp/install/lib/python/mercurial/dispatch.py", line 691, in runcommand
+      ret = _runcommand(ui, options, cmd, d)
+    File "/tmp/hgtests.5N93rp/install/lib/python/mercurial/dispatch.py", line 937, in _runcommand
+      return cmdfunc()
+    File "/tmp/hgtests.5N93rp/install/lib/python/mercurial/dispatch.py", line 926, in <lambda>
+      d = lambda: util.checksignature(func)(ui, *args, **strcmdopt)
+    File "/tmp/hgtests.5N93rp/install/lib/python/mercurial/util.py", line 1180, in check
+      return func(*args, **kwargs)
+    File "/tmp/hgtests.5N93rp/install/lib/python/hgext/releasenotes.py", line 580, in releasenotes
+      with open(file_, 'rb') as fh:
+  TypeError: coercing to Unicode: need string or buffer, NoneType found
+  [1]