How to pass parameter values that have spaces to the TortoiseMerge.exe command line?

I have two text files named "tmp1.txt" and "tmp2.txt". tmp1.txt just contains the text "Foo" and tmp2.txt just contains the text "Bar". When I execute the following command in Windows PowerShell:

TortoiseMerge.exe /base:"tmp1.txt" /basename:"Base: tmp1.txt" /mine:"tmp2.txt" /minename:"tmp2.txt"

I expect the title bar on the left panel of the TortoiseMerge window that pops up to be "Base: tmp1.txt", instead it just says "Base:". What am I doing wrong?

My TortoiseMerge version is: TortoiseMerge 1.14.6, Build 29673 - 64 Bit , 2023/12/25 19:33:34(I just installed the latest TortoiseSvn.)

I have tried the following variations for the "basename" parameter values:

1. tried: /basename:'Base: tmp1.txt' got: "Base:"expected: "Base: tmp1.txt"

2. tried: /basename:Base:\ tmp1.txtgot: Base:\expected: "Base: tmp1.txt"

Note: It's the spaces that are causing the problem. If I try the following variation: /basename:"Base:tmp1.txt" then I do see the text "Base:tmp1.txt" in TortoiseMerge's left panel title bar.