diff --git a/reasoning_gym/arithmetic/prime_factorization.py b/reasoning_gym/arithmetic/prime_factorization.py
index 5b4c6ecd..0a307284 100644
--- a/reasoning_gym/arithmetic/prime_factorization.py
+++ b/reasoning_gym/arithmetic/prime_factorization.py
@@ -49,7 +49,10 @@ class PrimeFactorizationDataset(ProceduralDataset):
 
     def _normalize_answer(self, answer: str) -> list[int]:
         """Parse and sort factors from a string"""
-        return sorted([int(factor.strip()) for factor in answer.split("×")])
+        if not answer or answer.strip() == "":
+            return []
+
+        return sorted([int(factor.strip()) for factor in answer.split("×") if factor.strip() != ""])
 
     def score_answer(self, answer: Optional[str], entry: dict[str, Any]) -> float:
         oracle_answer = entry["answer"]
diff --git a/tests/test_prime_factorization.py b/tests/test_prime_factorization.py
index a17bfa7a..389b89a4 100644
--- a/tests/test_prime_factorization.py
+++ b/tests/test_prime_factorization.py
@@ -119,6 +119,10 @@ def test_prime_factorization_score_answer():
     answer = None
     assert dataset.score_answer(answer, item) == 0.0
 
+    # Answer is empty string
+    answer = ""
+    assert dataset.score_answer(answer, item) == 0.01
+
 
 def is_prime(n: int) -> bool:
     """Helper function to check if a number is prime"""