Math Expression Node produces error if it calls a variable located within a hidden variable category

The math expression node in blueprints does not recognize variables that have been hidden within a blueprint category.

1. Open Editor (any project)
2. Create new blueprint
3. Create new int variable named "Test1"
4. In Details pane of variable>Category, enter "TestCategory"
5. In Class Settings>Hide Categories Press + button, add "TestCategory" to 0
6. In Event Graph, create a math expression node
7. In Math Expression node>Expression enter "Test1 + 1"
8. Compile

Results:

Error occurs:

Cannot access the blueprint's 'test1' variable from the expression 'test1+1'
Failed to generate argument #1 for the +function in 'test1+1'
No root node generated from the expression 'test1+1'
Failed to generate full expression graph for: 'test1+1'

Expected:

No error occurs, blueprint compiles.