diff --git a/lmformatenforcer/integrations/transformers.py b/lmformatenforcer/integrations/transformers.py
index 3dcfa60..0bdfd2f 100644
--- a/lmformatenforcer/integrations/transformers.py
+++ b/lmformatenforcer/integrations/transformers.py
@@ -1,5 +1,5 @@
 import functools
-from typing import Any, Callable, List, Tuple, Union
+from typing import Any, Callable, List, Optional, Tuple, Union
 try:
     from transformers import AutoModelForCausalLM
     from transformers.generation.logits_process import LogitsWarper, PrefixConstrainedLogitsProcessor
@@ -53,10 +53,10 @@ def unreplace_logits_warper(self):
         self.model._get_logits_warper = self.old_warper
 
 
-def _build_regular_tokens_list(tokenizer: PreTrainedTokenizerBase) -> List[Tuple[int, str, bool]]:
+def _build_regular_tokens_list(tokenizer: PreTrainedTokenizerBase, vocab_size: int) -> List[Tuple[int, str, bool]]:
     token_0 = tokenizer.encode("0")[-1]
     regular_tokens = []
-    for token_idx in range(len(tokenizer)):
+    for token_idx in range(vocab_size):
         if token_idx in tokenizer.all_special_ids:
             continue
         # We prepend token 0 and skip the first letter of the result to get a space if the token is a start word.
@@ -73,8 +73,10 @@ def _decode_function(tokenizer: PreTrainedTokenizerBase, tokens: List[int]) -> s
     return cleaned
 
 
-def build_token_enforcer_tokenizer_data(tokenizer: PreTrainedTokenizerBase) -> TokenEnforcerTokenizerData:
-    regular_tokens = _build_regular_tokens_list(tokenizer)
+def build_token_enforcer_tokenizer_data(tokenizer: PreTrainedTokenizerBase, 
+                                        vocab_size: Optional[int] = None) -> TokenEnforcerTokenizerData:
+    vocab_size = vocab_size or len(tokenizer)
+    regular_tokens = _build_regular_tokens_list(tokenizer, vocab_size)
     decode_fn = functools.partial(_decode_function, tokenizer)
     return TokenEnforcerTokenizerData(regular_tokens, decode_fn, tokenizer.eos_token_id)
 
diff --git a/lmformatenforcer/integrations/vllm.py b/lmformatenforcer/integrations/vllm.py
index b458757..94f6c2c 100644
--- a/lmformatenforcer/integrations/vllm.py
+++ b/lmformatenforcer/integrations/vllm.py
@@ -34,13 +34,16 @@ def __call__(self, input_ids: List[int], scores: torch.Tensor) -> torch.Tensor:
 
 def build_vllm_token_enforcer_tokenizer_data(tokenizer: Union[vllm.LLM, PreTrainedTokenizerBase]) -> TokenEnforcerTokenizerData:
     # There are many classes that can be passed here, this logic should work on all of them.
+    vocab_size = None
+    if hasattr(tokenizer, 'llm_engine'):
+        vocab_size = tokenizer.llm_engine.get_model_config().get_vocab_size()
     if hasattr(tokenizer, 'get_tokenizer'):
         tokenizer = tokenizer.get_tokenizer()
     if isinstance(tokenizer, MistralTokenizer):
-        return build_token_enforcer_tokenizer_data(tokenizer)
+        return build_token_enforcer_tokenizer_data(tokenizer, vocab_size)
     if hasattr(tokenizer, 'tokenizer'):
         tokenizer = tokenizer.tokenizer
-    return build_token_enforcer_tokenizer_data(tokenizer)
+    return build_token_enforcer_tokenizer_data(tokenizer, vocab_size)
 
 
 def build_vllm_logits_processor(llm: Union[vllm.LLM, PreTrainedTokenizerBase, TokenEnforcerTokenizerData],