Alt + Click Does Not Copy and Paste Layer Mask

Before version 2.6.0, I used to be able to press the Alt key and left click and drag a layer mask from one layer and drop it onto another, which would copy the layer mask from the first layer to the second layer. Now, I have to repeat that procedure to copy the mask. What happens is during the first drag and drop, I see that a layer mask is added to the second layer, even though it already has a white color filled layer mask. During the repeat operation, the copy succeeds, but the history panel shows a second instance of Add Layer Mask.