We get it: you’re lazy (or really efficient, depending on your point of view).

You’ve just kicked off a new project and have been tasked with building a new Microsoft Project schedule from the ground up. The thing is, your new project is so similar to the last project that you managed, that you’re tempted to copy your old project plan over, change a few dates and tasks, and call it done.

Everybody does it.

In most cases, you can get away with it, but if you ever need to report on several projects at once–say for a portfolio review meeting–this shortcut can come back and bite you, thanks to a little-known thing in Microsoft Project called the Project Summary Task.

The project summary task is the internal name of your project plan. In most cases, it’s identical to the name of your *.mpp file. Most people don’t even know it’s there, but if you’ve copied an old Microsoft Project plan over to create a new one, there’s a good chance that you forgot to change it. The fact that Microsoft hides the project summary task by default doesn’t help:

To make sure that your project has the correct name, go to Microsoft Project’s Format tab and check the Project Summary Task box. The project summary task will appear at line zero, right above all of the other tasks and milestones in your plan. If it turns out that you forgot to update it, you can change the name just like any other field in Microsoft Project.

Want to avoid this trouble in the future? Use Microsoft’s File > Save As feature instead of physically copying the file. When you save a project plan with a new name, Microsoft Project is smart enough to change the project summary task at the same time, which saves you the trouble of having to go back in and change it later.