diff --git a/outlines/fsm/guide.py b/outlines/fsm/guide.py
index 51b6e707e..fa824449a 100644
--- a/outlines/fsm/guide.py
+++ b/outlines/fsm/guide.py
@@ -118,9 +118,7 @@ def create_states_mapping(regex_string: str) -> Tuple[dict, set, set]:
                 regex_pattern.to_fsm().reduce(), keep_utf8=True
             )
             regex_fsm, _ = make_deterministic_fsm(byte_fsm)
-            states_to_token_maps, empty_token_ids = create_fsm_index_tokenizer(
-                regex_fsm, tokenizer
-            )
+            states_to_token_maps, _ = create_fsm_index_tokenizer(regex_fsm, tokenizer)
 
             # We make sure that it is possible to generate strings in the language
             # of the regular expression with the tokens present in the model's
@@ -133,11 +131,10 @@ def create_states_mapping(regex_string: str) -> Tuple[dict, set, set]:
                     "The vocabulary does not allow us to build a sequence that matches the input regex"
                 )
 
-            return states_to_token_maps, empty_token_ids, regex_fsm.finals
+            return states_to_token_maps, regex_fsm.finals
 
         (
             self.states_to_token_maps,
-            self.empty_token_ids,
             fsm_finals,
         ) = create_states_mapping(regex_string)
         self.eos_token_id = tokenizer.eos_token_id
@@ -218,9 +215,7 @@ def create_states_mapping_from_interegular_fsm(
             """
             byte_fsm = make_byte_level_fsm(fsm.reduce(), keep_utf8=True)
             regex_fsm, _ = make_deterministic_fsm(byte_fsm)
-            states_to_token_maps, empty_token_ids = create_fsm_index_tokenizer(
-                regex_fsm, tokenizer
-            )
+            states_to_token_maps, _ = create_fsm_index_tokenizer(regex_fsm, tokenizer)
 
             # We make sure that it is possible to generate strings in the language
             # of the regular expression with the tokens present in the model's
@@ -233,11 +228,10 @@ def create_states_mapping_from_interegular_fsm(
                     "The vocabulary does not allow us to build a sequence that matches the input regex"
                 )
 
-            return states_to_token_maps, empty_token_ids
+            return states_to_token_maps
 
         (
             from_interegular_instance.states_to_token_maps,
-            from_interegular_instance.empty_token_ids,
         ) = create_states_mapping_from_interegular_fsm(interegular_fsm)
         from_interegular_instance.eos_token_id = tokenizer.eos_token_id
         return from_interegular_instance
diff --git a/outlines/models/vllm.py b/outlines/models/vllm.py
index 378a35d91..038c80e60 100644
--- a/outlines/models/vllm.py
+++ b/outlines/models/vllm.py
@@ -1,7 +1,9 @@
+import concurrent.futures
 import dataclasses
 from typing import TYPE_CHECKING, List, Optional, Union
 
 from outlines.generate.api import GenerationParameters, SamplingParameters
+from outlines.integrations.utils import adapt_tokenizer
 
 if TYPE_CHECKING:
     from vllm import LLM
@@ -18,7 +20,7 @@ class VLLM:
 
     """
 
-    def __init__(self, model: "LLM"):
+    def __init__(self, model: "LLM", tokenizer):
         self.model = model
         self.lora_request = None
 
@@ -73,6 +75,9 @@ def generate(
         # are specified by the user when calling the generator.
         if max_tokens is not None:
             sampling_params.max_tokens = max_tokens
+        else:
+            sampling_params.max_tokens = None
+
         if stop_at is not None:
             if isinstance(stop_at, str):
                 stop_at = [stop_at]
@@ -140,7 +145,40 @@ def load_lora(self, adapter_path: Optional[str]):
             self.lora_request = LoRARequest(adapter_path, 1, adapter_path)
 
 
-def vllm(model_name: str, **vllm_model_params):
+def load_model(model_name, **vllm_model_params):
+    """Load the model in GPU memory."""
+    from vllm import LLM
+
+    model = LLM(model_name, **vllm_model_params)
+    return model
+
+
+def load_and_convert_tokenizer(model_name):
+    """Convert vocabulary types and JIT-compile function."""
+    from transformers import AutoTokenizer
+
+    tokenizer = AutoTokenizer.from_pretrained(model_name)
+    tokenizer = convert_tokenizer(tokenizer)
+    jit_compile_numba(tokenizer.numba_vocabulary)
+
+    return tokenizer
+
+
+def convert_tokenizer(tokenizer):
+    from outlines.fsm.regex import reduced_vocabulary
+
+    tokenizer = adapt_tokenizer(tokenizer)
+    vocabulary, _ = reduced_vocabulary(tokenizer)
+    tokenizer.vocabulary_numba = vocabulary
+
+    return tokenizer
+
+
+def jit_compile_numba(vocabulary):
+    pass
+
+
+def vllm(model_or_model_name: Union[str, "LLM"], **vllm_model_params):
     """Load a vLLM model.
 
     Arguments
@@ -154,6 +192,16 @@ def vllm(model_name: str, **vllm_model_params):
     """
     from vllm import LLM
 
-    model = LLM(model_name, **vllm_model_params)
+    if isinstance(model_or_model_name, LLM):
+        model = model_or_model_name
+        tokenizer = convert_tokenizer(model.tokenizer)
+    else:
+        with concurrent.futures.ThreadPoolExecutor() as executor:
+            model_name = model_or_model_name
+            future_model = executor.submit(load_model, model_name, **vllm_model_params)
+            future_tokenizer = executor.submit(load_and_convert_tokenizer, model_name)
+
+            tokenizer = future_tokenizer.result()
+            model = future_model.result()
 
-    return VLLM(model)
+    return VLLM(model, tokenizer)