diff --git a/mmcv/ops/deform_conv.py b/mmcv/ops/deform_conv.py
index 5c45bd4ebb..13ff04ea09 100644
--- a/mmcv/ops/deform_conv.py
+++ b/mmcv/ops/deform_conv.py
@@ -70,6 +70,7 @@ def forward(ctx,
         ctx.deform_groups = deform_groups
         ctx.im2col_step = im2col_step
 
+        weight = weight.type_as(input)
         ctx.save_for_backward(input, offset, weight)
 
         output = input.new_empty(