diff --git a/tools/preprocess_data.py b/tools/preprocess_data.py
index 13e5b64a47..4616810c26 100644
--- a/tools/preprocess_data.py
+++ b/tools/preprocess_data.py
@@ -73,6 +73,9 @@ def initializer(self):
 
         else:
             Encoder.splitter = IdentitySplitter()
+          
+        if Encoder.tokenizer.eod is None:
+            raise ValueError("EOD token is not set.")
 
     def split(self, json_line):
         data = json.loads(json_line)