diff --git a/Cargo.toml b/Cargo.toml
index c00e7ad..78db2dd 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -30,7 +30,7 @@ regex = "1.10.3"
 serde = "1.0.197"
 serde_json = "1.0.114"
 serde_with = "3.8.0"
-tokenizers = { version = "^0.21"}
+tokenizers = { version = "^0.23"}
 
 [dev-dependencies]
 tempfile = "3.10.1"
diff --git a/src/tokenizer.rs b/src/tokenizer.rs
index a6c53c5..67bed1d 100644
--- a/src/tokenizer.rs
+++ b/src/tokenizer.rs
@@ -349,7 +349,9 @@ impl SmirkTokenizer {
                 })
             })
             .collect::<Result<Vec<AddedToken>, PyErr>>()?;
-        Ok(self.tokenizer.add_tokens(&tokens))
+        self.tokenizer
+            .add_tokens(tokens)
+            .map_err(|e| PyValueError::new_err(e.to_string()))
     }
 
     #[pyo3(signature = (files, **kwargs))]