Prevent auto complete of non-executable files in path

[Alan <8fvebtoeq87@xxxxxxxxx>]

Hi,

I'm switching from bash to zsh (using version 5.8), and one thing that
bothers me is that zsh auto completes non-executable files in my $PATH.

For example:

$ echo $PATH
~/bin:/usr/local/bin:/usr/bin:/bin
$ ls -l ~/bin/
-rwx------    1 user staff     95 Jun  5  2019  asdf1
-rw-------    1 user staff     95 Jun  5  2019  asdf1~
-rwx------    1 user staff     95 Jun  5  2019  asdf2
-rw-------    1 user staff     95 Jun  5  2019  asdf3
$ asd<TAB>
external command
asdf1
asdf1\~
asdf2
asdf3

...whereas in bash, it would only auto complete asdf1 and asdf2 because
those are the only 2 files in ~/bin/ that are executable:

$ asd<TAB>
asdf1
asdf2

How can I get zsh to only auto complete executable files in the $PATH?

Thanks for your help, much appreciated!