diff --git a/qutebrowser/completion/completer.py b/qutebrowser/completion/completer.py
index 30a180554..4e187750d 100644
--- a/qutebrowser/completion/completer.py
+++ b/qutebrowser/completion/completer.py
@@ -87,8 +87,6 @@ class Completer(QObject):
             # cursor on a flag or after an explicit split (--)
             return None
         log.completion.debug("Before removing flags: {}".format(before_cursor))
-        before_cursor = [x for x in before_cursor if not x.startswith('-')]
-        log.completion.debug("After removing flags: {}".format(before_cursor))
         if not before_cursor:
             # '|' or 'set|'
             log.completion.debug('Starting command completion')
@@ -99,6 +97,9 @@ class Completer(QObject):
             log.completion.debug("No completion for unknown command: {}"
                                  .format(before_cursor[0]))
             return None
+
+        before_cursor = [x for x in before_cursor if not x.startswith('-')]
+        log.completion.debug("After removing flags: {}".format(before_cursor))
         argpos = len(before_cursor) - 1
         try:
             func = cmd.get_pos_arg_info(argpos).completion
diff --git a/tests/unit/completion/test_completer.py b/tests/unit/completion/test_completer.py
index e25d4e5d1..4b39b7032 100644
--- a/tests/unit/completion/test_completer.py
+++ b/tests/unit/completion/test_completer.py
@@ -190,6 +190,7 @@ def _set_cmd_prompt(cmd, txt):
     (':gibberish nonesense |', None, '', []),
     ('/:help|', None, '', []),
     ('::bind|', 'command', ':bind', []),
+    (':-w open |', None, '', []),
 ])
 def test_update_completion(txt, kind, pattern, pos_args, status_command_stub,
                            completer_obj, completion_widget_stub, config_stub,