diff --git a/detection/backbonev2.py b/detection/backbonev2.py
index 647c73e..7a35cb4 100644
--- a/detection/backbonev2.py
+++ b/detection/backbonev2.py
@@ -668,7 +668,7 @@ def forward(self, x):
             if not self.training:
                 cls_out = (cls_out[0] + cls_out[1]) / 2
         else:
-            cls_out = self.head(x.mean(-2))
+            cls_out = self.head(x.flatten(2).mean(-1))
         # for image classification
         return cls_out