diff --git a/mindarmour/diff_privacy/evaluation/membership_inference.py b/mindarmour/diff_privacy/evaluation/membership_inference.py
index 3e53c8f1cba18d6e4f7f6460e306fea0eaad96f6..c0f802e916f70d2a195e71767d218af09f217ac2 100644
--- a/mindarmour/diff_privacy/evaluation/membership_inference.py
+++ b/mindarmour/diff_privacy/evaluation/membership_inference.py
@@ -41,7 +41,7 @@ def _eval_info(pred, truth, option):
         ValueError, size of parameter pred or truth is 0.
         ValueError, value of parameter option must be in ["precision", "accuracy", "recall"].
     """
-    if pred.size == 0 || truth.size == 0:
+    if pred.size == 0 or truth.size == 0:
         raise ValueError("Size of pred or truth is 0.")
 
     if option == "accuracy":