diff --git a/gguf-py/gguf/vocab.py b/gguf-py/gguf/vocab.py
index 36fc5cf023..b554dab7c5 100644
--- a/gguf-py/gguf/vocab.py
+++ b/gguf-py/gguf/vocab.py
@@ -164,7 +164,7 @@ class SpecialVocab:
         if normalizer_type == 'Lowercase':
             self.normalizer_lowercase = True
         elif normalizer_type == 'BertNormalizer':
-            if normalizer.get('lowercase', False):
+            if normalizer.get('lowercase', True):
                 self.normalizer_lowercase = True
         elif normalizer_type == 'Sequence':
             for norm in normalizer.get('normalizers', []):