diff --git a/olmocr/bench/tests.py b/olmocr/bench/tests.py
index 85bab99..2e2ac64 100644
--- a/olmocr/bench/tests.py
+++ b/olmocr/bench/tests.py
@@ -38,6 +38,9 @@ class ValidationError(Exception):
 
 
 def normalize_text(md_content: str) -> str:
+    if md_content is None:
+        return None
+
     # Normalize whitespace in the md_content
     md_content = re.sub(r"\s+", " ", md_content)