diff --git a/vllm/model_executor/models/registry.py b/vllm/model_executor/models/registry.py
index 81623defd337..bae6444267fa 100644
--- a/vllm/model_executor/models/registry.py
+++ b/vllm/model_executor/models/registry.py
@@ -347,6 +347,10 @@ def register_model(
           when importing the model and thus the related error
           :code:`RuntimeError: Cannot re-initialize CUDA in forked subprocess`.
         """
+        if not isinstance(model_arch, str):
+            msg = f"`model_arch` should be a string, not a {type(model_arch)}"
+            raise TypeError(msg)
+
         if model_arch in self.models:
             logger.warning(
                 "Model architecture %s is already registered, and will be "
@@ -360,8 +364,18 @@ def register_model(
                 raise ValueError(msg)
 
             model = _LazyRegisteredModel(*split_str)
-        else:
+
+            try:
+                model.inspect_model_cls()
+            except Exception as exc:
+                msg = f"Unable to inspect model {model_cls}"
+                raise RuntimeError(msg) from exc
+        elif isinstance(model_cls, type) and issubclass(model_cls, nn.Module):
             model = _RegisteredModel.from_model_cls(model_cls)
+        else:
+            msg = ("`model_cls` should be a string or PyTorch model class, "
+                   f"not a {type(model_arch)}")
+            raise TypeError(msg)
 
         self.models[model_arch] = model