diff --git a/tokenizers/src/models/bpe/model.rs b/tokenizers/src/models/bpe/model.rs
index d46118b0..6cb34fe1 100644
--- a/tokenizers/src/models/bpe/model.rs
+++ b/tokenizers/src/models/bpe/model.rs
@@ -1,5 +1,5 @@
 use super::{Cache, Error, Pair, Word};
-use crate::tokenizer::{Model, Token};
+use crate::tokenizer::{Model, Result, Token};
 use serde_json::Value;
 use std::{
     collections::HashMap,
@@ -37,7 +37,7 @@ impl BPE {
         BPE::new(HashMap::new(), HashMap::new(), HashMap::new())
     }
 
-    pub fn from_files(vocab: &str, merges: &str) -> Result<Self, Error> {
+    pub fn from_files(vocab: &str, merges: &str) -> Result<Self> {
         // Read vocab.json
         let vocab_file = File::open(vocab)?;
         let mut vocab_file = BufReader::new(vocab_file);
@@ -55,7 +55,7 @@ impl BPE {
                     }
                 }
             }
-            _ => return Err(Error::BadVocabulary),
+            _ => return Err(Box::new(Error::BadVocabulary)),
         };
 
         // Read merges file
@@ -100,9 +100,9 @@ impl Model for BPE {
         self.vocab.len()
     }
 
-    fn tokenize(&self, sentence: Vec<String>) -> Vec<Token> {
+    fn tokenize(&self, sentence: Vec<String>) -> Result<Vec<Token>> {
         if sentence.len() == 0 {
-            return vec![];
+            return Ok(vec![]);
         }
 
         let mut encoded: Vec<Token> = Vec::with_capacity(sentence.len());
@@ -181,15 +181,16 @@ impl Model for BPE {
             .unzip::<_, _, Vec<String>, Vec<Word>>();
         self.cache.set_values(keys, values);
 
-        encoded
+        Ok(encoded)
     }
 
-    fn decode(&self, ids: Vec<u32>) -> Vec<String> {
-        ids.into_iter()
+    fn decode(&self, ids: Vec<u32>) -> Result<Vec<String>> {
+        Ok(ids
+            .into_iter()
             .map(|id| self.vocab_r.get(&id))
             .filter(|token| token.is_some())
             .map(|id| id.unwrap().clone())
-            .collect()
+            .collect())
     }
 
     fn token_to_id(&self, token: &str) -> Option<u32> {
diff --git a/tokenizers/src/models/bpe/trainer.rs b/tokenizers/src/models/bpe/trainer.rs
index d9310aa2..b1234e33 100644
--- a/tokenizers/src/models/bpe/trainer.rs
+++ b/tokenizers/src/models/bpe/trainer.rs
@@ -4,10 +4,9 @@
 //! In charge of training a BPE model
 //!
 use super::{Pair, Word, BPE};
-use crate::tokenizer::{Model, Trainer};
+use crate::tokenizer::{Model, Result, Trainer};
 use std::{
     collections::{HashMap, HashSet},
-    error::Error,
     time::Instant,
 };
 
@@ -50,10 +49,7 @@ impl BpeTrainer {
 
 impl Trainer for BpeTrainer {
     /// Train a BPE model
-    fn train(
-        &self,
-        word_counts: HashMap<String, u32>,
-    ) -> Result<Box<dyn Model + Sync>, Box<dyn Error>> {
+    fn train(&self, word_counts: HashMap<String, u32>) -> Result<Box<dyn Model + Sync>> {
         let mut words: Vec<Word> = vec![];
         let mut counts: Vec<i32> = vec![];
         let mut word_to_id: HashMap<String, u32> = HashMap::new();
diff --git a/tokenizers/src/pre_tokenizers/byte_level.rs b/tokenizers/src/pre_tokenizers/byte_level.rs
index c4bef007..04b03f8c 100644
--- a/tokenizers/src/pre_tokenizers/byte_level.rs
+++ b/tokenizers/src/pre_tokenizers/byte_level.rs
@@ -1,4 +1,4 @@
-use crate::tokenizer::{Decoder, PreTokenizer};
+use crate::tokenizer::{Decoder, PreTokenizer, Result};
 use regex::Regex;
 use std::collections::HashMap;
 
@@ -32,8 +32,9 @@ lazy_static! {
 
 pub struct ByteLevel;
 impl PreTokenizer for ByteLevel {
-    fn pre_tokenize(&self, s: &str) -> Vec<String> {
-        RE.captures_iter(s)
+    fn pre_tokenize(&self, s: &str) -> Result<Vec<String>> {
+        Ok(RE
+            .captures_iter(s)
             .map(|capture| {
                 let capture = capture.get(0).unwrap();
                 let start = capture.start();
@@ -78,20 +79,20 @@ impl PreTokenizer for ByteLevel {
                     .map(|b| std::char::from_u32(BYTES_CHAR[b]).unwrap())
                     .collect()
             })
-            .collect()
+            .collect())
     }
 }
 
 impl Decoder for ByteLevel {
-    fn decode(&self, tokens: Vec<String>) -> String {
-        String::from_utf8_lossy(
+    fn decode(&self, tokens: Vec<String>) -> Result<String> {
+        Ok(String::from_utf8_lossy(
             &tokens
                 .join("")
                 .chars()
                 .map(|c| CHAR_BYTES[&(c as u32)])
                 .collect::<Vec<_>>(),
         )
-        .into_owned()
+        .into_owned())
     }
 }
 
@@ -104,7 +105,9 @@ mod tests {
     fn pre_tokenization() {
         let pre_tok = ByteLevel;
         assert_eq!(
-            pre_tok.pre_tokenize("Hello my friend, how is your day going?"),
+            pre_tok
+                .pre_tokenize("Hello my friend, how is your day going?")
+                .unwrap(),
             vec![
                 "Hello", "Ġmy", "Ġfriend", ",", "Ġhow", "Ġis", "Ġyour", "Ġday", "Ġgoing", "?"
             ]
@@ -116,14 +119,17 @@ mod tests {
         let decoder = ByteLevel;
         assert_eq!(
             "Hello my friend, how is your day going?",
-            decoder.decode(
-                vec![
-                    "Hello", "Ġmy", "Ġfriend", ",", "Ġhow", "Ġis", "Ġyour", "Ġday", "Ġgoing", "?"
-                ]
-                .into_iter()
-                .map(|s| s.into())
-                .collect::<Vec<String>>()
-            )
+            decoder
+                .decode(
+                    vec![
+                        "Hello", "Ġmy", "Ġfriend", ",", "Ġhow", "Ġis", "Ġyour", "Ġday", "Ġgoing",
+                        "?"
+                    ]
+                    .into_iter()
+                    .map(|s| s.into())
+                    .collect::<Vec<String>>()
+                )
+                .unwrap()
         );
     }
 
@@ -141,13 +147,13 @@ mod tests {
 
         let bl = ByteLevel;
         for sample in samples {
-            let pre_tokenized = bl.pre_tokenize(&sample);
+            let pre_tokenized = bl.pre_tokenize(&sample).unwrap();
             let separated_tokens = pre_tokenized
                 .into_iter()
                 .map(|token| token.split("").map(|t| t.into()).collect::<Vec<_>>())
                 .flatten()
                 .collect::<Vec<_>>();
-            assert_eq!(sample, bl.decode(separated_tokens));
+            assert_eq!(sample, bl.decode(separated_tokens).unwrap());
         }
     }
 }