diff --git a/typer/main.py b/typer/main.py
index 9db26975ca..4b3923e14b 100644
--- a/typer/main.py
+++ b/typer/main.py
@@ -504,7 +504,7 @@ def get_group_from_info(
         context_param_name,
     ) = get_params_convertors_ctx_param_name_from_function(solved_info.callback)
     cls = solved_info.cls or TyperGroup
-    assert issubclass(cls, TyperGroup)
+    assert issubclass(cls, TyperGroup), f"{cls} should be a subclass of {TyperGroup}"
     group = cls(
         name=solved_info.name or "",
         commands=commands,