diff --git a/brew/selection/dynamic/mcb.py b/brew/selection/dynamic/mcb.py
index 35abfb9..fd979c5 100644
--- a/brew/selection/dynamic/mcb.py
+++ b/brew/selection/dynamic/mcb.py
@@ -92,7 +92,7 @@ def select(self, ensemble, x):
         # use best_classifier
         best_i = np.argmax(scores)
         best_j_score = np.max(scores[np.arange(len(scores)) != best_i])
-        if scores[best_i] - scores[best_j] >= self.significance_threshold:
+        if scores[best_i] - scores[best_j_score] >= self.significance_threshold:
             best_classifier = ensemble.classifiers[best_i]
             return Ensemble(classifiers=[best_classifier]), None