zsh completion doesn't work when prepending to word

I have two versions of a certain application, the one in my PATH and one at ~/install/app. So normally I do

app file

But sometimes I want to do, right after that:

~/install/app file

With bash I would

app fileESCI to position the cursor in the begining of the line (I use vim keybindings)

Then, with the cursor in the begiing of the line, start typing ~/install and complete with TAB:

~/insTABapp file

~/install/app file

However, with zsh the completion does not work, because there is no space between ~/ins and app, so it doesn't know what to do. How can I solve this?