diff --git a/hgext/convert/subversion.py b/hgext/convert/subversion.py
--- a/hgext/convert/subversion.py
+++ b/hgext/convert/subversion.py
@@ -178,7 +178,7 @@ def issvnurl(ui, url):
         path = os.path.abspath(url)
     if proto == 'file':
         path = path.replace(os.sep, '/')
-    check = protomap.get(proto, lambda p, p2: False)
+    check = protomap.get(proto, lambda *args: False)
     while '/' in path:
         if check(ui, path, proto):
             return True
diff --git a/tests/test-convert b/tests/test-convert
--- a/tests/test-convert
+++ b/tests/test-convert
@@ -62,4 +62,7 @@ hg convert a b
 echo % "contents of fncache file:"
 cat b/.hg/store/fncache
 
+echo '% test bogus URL'
+hg convert -q bzr+ssh://foobar@selenic.com/baz baz
+
 true
diff --git a/tests/test-convert.out b/tests/test-convert.out
--- a/tests/test-convert.out
+++ b/tests/test-convert.out
@@ -287,3 +287,5 @@ 0 e
 % contents of fncache file:
 data/a.i
 data/b.i
+% test bogus URL
+abort: bzr+ssh://foobar@selenic.com/baz: missing or unsupported repository