diff --git a/vllm/engine/multiprocessing/engine.py b/vllm/engine/multiprocessing/engine.py
index 33b96af3018a3..739cbedc2f8cc 100644
--- a/vllm/engine/multiprocessing/engine.py
+++ b/vllm/engine/multiprocessing/engine.py
@@ -29,6 +29,8 @@ from vllm.engine.multiprocessing import (ENGINE_DEAD_ERROR, IPC_DATA_EXT,
 # yapf: enable
 from vllm.logger import init_logger
 from vllm.outputs import RequestOutput
+from vllm.transformers_utils.config import (
+    maybe_register_config_serialize_by_value)
 from vllm.usage.usage_lib import UsageContext
 from vllm.worker.model_runner_base import InputProcessingError
 
@@ -42,12 +44,12 @@ class MQLLMEngine:
     """A multiprocessing wrapper for :class:`LLMEngine`.
 
     This class is used to wrap the :class:`LLMEngine` class to enable use
-    in concurrnet manner. It runs a background loop and uses zeromq to 
+    in concurrnet manner. It runs a background loop and uses zeromq to
     receive new requests and stream outputs incrementally via ipc.
-    
+
     The :class:`LLMEngine` generate or encode process is kicked off when a new
     RPCProcessRequest is received by the input_socket.
-    
+
     The self.engine_loop checks the input_socket for new requests,
     adds them to the LLMEngine if there are any, calls the internal
     :class:`LLMEngine.step()`, and sends the RequestOutputs back over
@@ -428,6 +430,9 @@ def run_mp_engine(vllm_config: VllmConfig, usage_context: UsageContext,
                   ipc_path: str, disable_log_stats: bool,
                   disable_log_requests: bool, engine_alive):
     try:
+        # Ensure we can serialize transformer config before spawning
+        maybe_register_config_serialize_by_value()
+
         engine = MQLLMEngine.from_vllm_config(
             vllm_config=vllm_config,
             usage_context=usage_context,
diff --git a/vllm/entrypoints/openai/api_server.py b/vllm/entrypoints/openai/api_server.py
index bc74ebd205d15..ef557193ae2a6 100644
--- a/vllm/entrypoints/openai/api_server.py
+++ b/vllm/entrypoints/openai/api_server.py
@@ -82,6 +82,8 @@ from vllm.entrypoints.openai.serving_transcription import (
 from vllm.entrypoints.openai.tool_parsers import ToolParserManager
 from vllm.entrypoints.utils import load_aware_call, with_cancellation
 from vllm.logger import init_logger
+from vllm.transformers_utils.config import (
+    maybe_register_config_serialize_by_value)
 from vllm.usage.usage_lib import UsageContext
 from vllm.utils import (FlexibleArgumentParser, get_open_zmq_ipc_path,
                         is_valid_ipv6_address, set_ulimit)
@@ -221,6 +223,9 @@ async def build_async_engine_client_from_engine_args(
         # so we need to spawn a new process
         context = multiprocessing.get_context("spawn")
 
+        # Ensure we can serialize transformer config before spawning
+        maybe_register_config_serialize_by_value()
+
         # The Process can raise an exception during startup, which may
         # not actually result in an exitcode being reported. As a result
         # we use a shared variable to communicate the information.