diff --git a/lib/completion.zsh b/lib/completion.zsh
index fa1d97f48..4cb4e3678 100644
--- a/lib/completion.zsh
+++ b/lib/completion.zsh
@@ -25,7 +25,7 @@ bindkey -M menuselect '^o' accept-and-infer-next-history
 
 zstyle ':completion:*:*:*:*:*' menu select
 zstyle ':completion:*:*:kill:*:processes' list-colors '=(#b) #([0-9]#) ([0-9a-z-]#)*=01;34=0=01'
-zstyle ':completion:*:*:*:*:processes' command "ps -u `whoami` -o pid,user,comm -w -w"
+zstyle ':completion:*:*:*:*:processes' command "ps -u $(whoami) -o pid,user,comm -w -w"
 
 # disable named-directories autocompletion
 zstyle ':completion:*:cd:*' tag-order local-directories directory-stack path-directories