When Theme Developer turned on, can't add content to panels

This is non-critical, so I didn't do screenshots, etc., & in fact, may belong in the Devel module issue queue instead, but I wanted to report it in case others experience the same thing & turn to the Panels issue queue to find an answer. After I turned on Theme Devel, the normal "gear" to the left of the panel pane that allows you to "Add content" would no longer appear. Simply turning off the Theme Devel module seemed to resolve the issue for me.