The Default Value for a Timespan variable resets whenever its Blueprint is compiled

The Default Value for a Timespan variable resets to 00:00:00.000 whenever its Blueprint is compiled.

1. Launch: UE4Editor.exe (any project)
2. Create a new Actor Blueprint
3. Create a new variable of type Timespan
4. Compile
5. Enter a Default Value of anything other than 00:00:00.000
6. Compile

Results:
The Default Value reverts to 00:00:00.000 whenever the BP is compiled.