diff --git a/curated_transformers/tokenizers/legacy/bbpe_tokenizer.py b/curated_transformers/tokenizers/legacy/bbpe_tokenizer.py
index 79a842b3..b60ca437 100644
--- a/curated_transformers/tokenizers/legacy/bbpe_tokenizer.py
+++ b/curated_transformers/tokenizers/legacy/bbpe_tokenizer.py
@@ -64,7 +64,7 @@ def _encode(self, input: Iterable[MergedInputChunks]) -> PiecesWithIds:
 
             for chunk in seq:
                 if isinstance(chunk, MergedSpecialPieceChunk):
-                    piece_id = self.processor.piece_id(chunk.piece)
+                    piece_id = self.processor.piece_to_id(chunk.piece)
                     if piece_id is None:
                         raise ValueError(f"Unknown special piece: {chunk.piece}")
                     seq_ids.append(piece_id)
diff --git a/curated_transformers/tokenizers/legacy/roberta_tokenizer.py b/curated_transformers/tokenizers/legacy/roberta_tokenizer.py
index 5f0b328e..dcc3441a 100644
--- a/curated_transformers/tokenizers/legacy/roberta_tokenizer.py
+++ b/curated_transformers/tokenizers/legacy/roberta_tokenizer.py
@@ -131,7 +131,7 @@ def _load_from_vocab_files(
 
 
 def _get_piece_id_or_fail(processor: ByteBPEProcessor, piece: str):
-    piece_id = processor.piece_id(piece)
+    piece_id = processor.piece_to_id(piece)
     if piece_id is None:
         raise ValueError(
             f"RoBERTa piece encoder vocabulary doesn't contain '{piece}' piece"
diff --git a/curated_transformers/tokenizers/legacy/sentencepiece_tokenizer.py b/curated_transformers/tokenizers/legacy/sentencepiece_tokenizer.py
index 7053143f..279c03a5 100644
--- a/curated_transformers/tokenizers/legacy/sentencepiece_tokenizer.py
+++ b/curated_transformers/tokenizers/legacy/sentencepiece_tokenizer.py
@@ -52,12 +52,8 @@ def _encode(self, input: Iterable[MergedInputChunks]) -> PiecesWithIds:
 
             for chunk in seq:
                 if isinstance(chunk, MergedSpecialPieceChunk):
-                    # TODO: this is not ideal. piece_id() should probably return
-                    # None for unknown pieces.
-                    unk_id = self.processor.unk_id()
-                    unk_piece = self.processor.id_to_piece(unk_id)
                     piece_id = self.processor.piece_to_id(chunk.piece)
-                    if piece_id == unk_id and chunk.piece != unk_piece:
+                    if piece_id is None:
                         raise ValueError(f"Unknown special piece: {chunk.piece}")
                     seq_ids.append(piece_id)
                     seq_pieces.append(chunk.piece)
diff --git a/requirements.txt b/requirements.txt
index ccb00791..458cbf3e 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,4 +1,4 @@
-curated-tokenizers>=0.0.7,<0.1.0
+curated-tokenizers>=0.9.0.dev0,<1.0.0
 huggingface-hub>=0.14
 tokenizers>=0.13.3
 torch>=1.12.0
diff --git a/setup.cfg b/setup.cfg
index 2854e618..4d352212 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -14,7 +14,7 @@ zip_safe = true
 include_package_data = true
 python_requires = >=3.8
 install_requires =
-    curated-tokenizers>=0.0.7,<0.1.0
+    curated-tokenizers>=0.9.0.dev0,<1.0.0
     huggingface-hub>=0.14
     tokenizers>=0.13.3
     torch>=1.12.0