diff --git a/aider/commands.py b/aider/commands.py
index 47829aa04..4ded7fe8a 100644
--- a/aider/commands.py
+++ b/aider/commands.py
@@ -1089,13 +1089,16 @@ class Commands:
         )
 
     def completions_ask(self):
-        raise NotImplementedError("Use normal autocompleter")
+        from aider.io import CommandCompletionException
+        raise CommandCompletionException()
 
     def completions_code(self):
-        raise NotImplementedError("Use normal autocompleter")
+        from aider.io import CommandCompletionException
+        raise CommandCompletionException()
 
     def completions_architect(self):
-        raise NotImplementedError("Use normal autocompleter")
+        from aider.io import CommandCompletionException
+        raise CommandCompletionException()
 
     def cmd_ask(self, args):
         """Ask questions about the code base without editing any files. If no prompt provided, switches to ask mode."""  # noqa
diff --git a/aider/io.py b/aider/io.py
index f7ffa3306..ffb364e23 100644
--- a/aider/io.py
+++ b/aider/io.py
@@ -187,9 +187,12 @@ class AutoCompleter(Completer):
             return
 
         if text[0] == "/":
-            # catch and handle here; make a purpose built exception for this. ai!
-            yield from self.get_command_completions(document, complete_event, text, words)
-            return
+            try:
+                yield from self.get_command_completions(document, complete_event, text, words)
+                return
+            except CommandCompletionException:
+                # Fall through to normal completion
+                pass
 
         candidates = self.words
         candidates.update(set(self.fname_to_rel_fnames))