diff --git a/utils/utils.py b/utils/utils.py
index bccb4278..fe620193 100755
--- a/utils/utils.py
+++ b/utils/utils.py
@@ -99,15 +99,20 @@ def ap_per_class(tp, conf, pred_cls, target_cls):
     tp, conf, pred_cls = tp[i], conf[i], pred_cls[i]
 
     # Find unique classes
-    unique_classes = target_cls #np.unique(np.concatenate((pred_cls, target_cls), 0))
+    unique_classes = np.unique(np.concatenate((pred_cls, target_cls), 0))
 
     # Create Precision-Recall curve and compute AP for each class
     ap = []
     for c in unique_classes:
         i = pred_cls == c
         n_gt = sum(target_cls == c)  # Number of ground truth objects
+        n_p = sum(i)  # Number of predicted objects
 
-        if sum(i) == 0:
+        if (n_p == 0) and (n_gt == 0):
+            continue
+        elif (np == 0) and (n_gt > 0):
+            ap.append(0)
+        elif (n_p > 0) and (n_gt == 0):
             ap.append(0)
         else:
             # Accumulate FPs and TPs