diff --git a/mmdet/models/necks/fpn.py b/mmdet/models/necks/fpn.py
index 2f065ed0dbb..9f601386549 100644
--- a/mmdet/models/necks/fpn.py
+++ b/mmdet/models/necks/fpn.py
@@ -165,11 +165,12 @@ def forward(self, inputs):
             # In some cases, fixing `scale factor` (e.g. 2) is preferred, but
             #  it cannot co-exist with `size` in `F.interpolate`.
             if 'scale_factor' in self.upsample_cfg:
-                laterals[i - 1] += F.interpolate(laterals[i],
-                                                 **self.upsample_cfg)
+                # fix runtime error of "+=" inplace operation in PyTorch 1.10
+                laterals[i - 1] = laterals[i - 1] + F.interpolate(
+                    laterals[i], **self.upsample_cfg)
             else:
                 prev_shape = laterals[i - 1].shape[2:]
-                laterals[i - 1] += F.interpolate(
+                laterals[i - 1] = laterals[i - 1] + F.interpolate(
                     laterals[i], size=prev_shape, **self.upsample_cfg)
 
         # build outputs