diff --git a/utils/metrics.py b/utils/metrics.py
index 6bba4cfe2a42..9bf084c78854 100644
--- a/utils/metrics.py
+++ b/utils/metrics.py
@@ -139,6 +139,12 @@ def process_batch(self, detections, labels):
         Returns:
             None, updates confusion matrix accordingly
         """
+        if detections is None:
+            gt_classes = labels.int()
+            for i, gc in enumerate(gt_classes):
+                self.matrix[self.nc, gc] += 1  # background FN
+            return
+
         detections = detections[detections[:, 4] > self.conf]
         gt_classes = labels[:, 0].int()
         detection_classes = detections[:, 5].int()
diff --git a/val.py b/val.py
index b0cc8e7f1577..48207a1130a6 100644
--- a/val.py
+++ b/val.py
@@ -228,6 +228,8 @@ def run(
             if npr == 0:
                 if nl:
                     stats.append((correct, *torch.zeros((2, 0), device=device), labels[:, 0]))
+                    if plots:
+                        confusion_matrix.process_batch(detections=None, labels=labels[:, 0])
                 continue
 
             # Predictions