Macro Stop Working With No Error

I have wrote a simple macro/ function that used to work before I decided to improve it. When I run the macro, I can step F8 until the before last line in the following code

Function bla() As Boolean
Set rCell = Cells(1, 1)
If rCell.Value <> "" Then
x = rCell.Value * 0.02 'Works
rCell.Value = rCell.Value - x 'Doesn't work
End If
bla = False
End Function

Excel does stop running the macro, but it doesn't show any error so I don't know what to fix.
Steps to reproduce the problem:
1. Create new Excel document
2. Type any number in the very first cell
3. Open VBA, add module and copy above function
4. Type in another cell "=bla()"