Colon in alias appears to be breaking task compltion

[Steve Dondley <s@xxxxxxxxxxx>]

My alias A for taskwarrior:
alias taa='task +st +sn add'

My alias B for taskwarrior:
alias tai="task +imm +st due:1h add"

Alias A works fine with tab completion. "taa proj<tab>" completes the 
word "project" as expected.

Alias B does not work: with "tai proj<tab>" there is no tab completion 
for the word "project".

I can get alias B to work if I remove the "due:1h" bit from the right 
hand side of Alias B. So it appears the colon is causing issues.

Workaround?