diff --git a/liquidprompt b/liquidprompt
index 93bde0e..096fb93 100755
--- a/liquidprompt
+++ b/liquidprompt
@@ -1673,7 +1673,7 @@ _lp_set_prompt()
         source "$LP_PS1_FILE"
     fi
 
-    if [ "$_LP_SHELL_zsh" ] ; then
+    if $_LP_SHELL_zsh; then
         # If ZSH, use PS1 and RPS1
         if [[ -z "$LP_PS1" ]] ; then
             # add title, host, and permissions colon