diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 7534ae55907..4d8e60d3929 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -58,7 +58,8 @@ repos:
     entry: tools/mypy.sh 0 "local"
     language: python
     types: [python]
-    additional_dependencies: &mypy_deps [mypy==1.11.1, types-cachetools, types-setuptools, types-PyYAML, types-requests, pydantic]
+    additional_dependencies: &mypy_deps [mypy==1.16.0, types-cachetools,
+                                         types-setuptools, types-PyYAML, types-requests, pydantic]
     stages: [pre-commit] # Don't run in CI
   - id: mypy-3.9 # TODO: Use https://github.com/pre-commit/mirrors-mypy when mypy setup is less awkward
     name: Run mypy for Python 3.9
diff --git a/vllm/entrypoints/openai/tool_parsers/hermes_tool_parser.py b/vllm/entrypoints/openai/tool_parsers/hermes_tool_parser.py
index c7030d34d45..a225180e055 100644
--- a/vllm/entrypoints/openai/tool_parsers/hermes_tool_parser.py
+++ b/vllm/entrypoints/openai/tool_parsers/hermes_tool_parser.py
@@ -237,7 +237,6 @@ def extract_tool_calls_streaming(
                 return delta
 
             try:
-
                 current_tool_call = partial_json_parser.loads(
                     tool_call_portion or "{}",
                     flags) if tool_call_portion else None
@@ -252,7 +251,7 @@ def extract_tool_calls_streaming(
             # case - we haven't sent the tool name yet. If it's available, send
             #   it. otherwise, wait until it's available.
             if not self.current_tool_name_sent:
-                if (current_tool_call is None):
+                if current_tool_call is None:
                     return None
                 function_name: Union[str, None] = current_tool_call.get("name")
                 if function_name:
@@ -292,6 +291,8 @@ def extract_tool_calls_streaming(
             #   JSON to the current partially-parsed JSON
             prev_arguments = (
                 self.prev_tool_call_arr[self.current_tool_id].get("arguments"))
+            if current_tool_call is None:
+                return None
             cur_arguments = current_tool_call.get("arguments")
 
             logger.debug("diffing old arguments: %s", prev_arguments)
@@ -359,9 +360,13 @@ def extract_tool_calls_streaming(
             # handle saving the state for the current tool into
             # the "prev" list for use in diffing for the next iteration
             if self.current_tool_id == len(self.prev_tool_call_arr) - 1:
+                if current_tool_call is None:
+                    return None
                 self.prev_tool_call_arr[self.current_tool_id] = \
                     current_tool_call
             else:
+                if current_tool_call is None:
+                    return None
                 self.prev_tool_call_arr.append(current_tool_call)
 
             return delta
diff --git a/vllm/sampling_params.py b/vllm/sampling_params.py
index a9a862384d1..929b5cf5d52 100644
--- a/vllm/sampling_params.py
+++ b/vllm/sampling_params.py
@@ -489,7 +489,8 @@ def update_from_generation_config(
             if eos_ids:
                 self._all_stop_token_ids.update(eos_ids)
                 if not self.ignore_eos:
-                    eos_ids.update(self.stop_token_ids)
+                    if self.stop_token_ids is not None:
+                        eos_ids.update(self.stop_token_ids)
                     self.stop_token_ids = list(eos_ids)
 
     def update_from_tokenizer(self, tokenizer: AnyTokenizer) -> None: