Using Certain Names in Blueprint Math Expression Causes Compiler Error

Entering a value such as x1-x0 into a math expression node is causing a compiler error in blueprints.

This is inconsistent with the behavior in 4.12.5, when entering the same expression would cause no error. This is a regression.

1. Open the editor
2. Create a new actor blueprint
3. Right-click and search for Add Math Expression
4. When the node appears, type in x0
5. Compile

Result: Error message appears along the lines of:

Expected: Behavior would be consistent with 4.12.5 and no error would appear.