diff --git a/outlines/fsm/regex.py b/outlines/fsm/regex.py
index 8dbbd79b1..b83d1f11b 100644
--- a/outlines/fsm/regex.py
+++ b/outlines/fsm/regex.py
@@ -825,6 +825,12 @@ def reduced_vocabulary(
         )
     )
     for token_tuple, token_ids in vocabulary.items():
+        # numpy doesn't track null bytes in arrays
+        # np.fromiter('\x00' ...) results in an empty string [""]
+        # https://github.com/numpy/numpy/issues/26275
+        if token_tuple == "\x00":
+            continue
+
         token_tuple_np = np.fromiter(token_tuple, dtype=np.dtype("U2"))
         token_ids_np = np.fromiter(token_ids, dtype=np.dtype("int64"))
         vocabulary_nb.append((token_tuple_np, token_ids_np))