diff --git a/lib/preexec.bash b/lib/preexec.bash
index c2c00e0f..1223ce0e 100644
--- a/lib/preexec.bash
+++ b/lib/preexec.bash
@@ -1,4 +1,4 @@
-#!/usr/bin/env
+#!/usr/bin/env bash
 
 # bash-preexec.sh -- Bash support for ZSH-like 'preexec' and 'precmd' functions.
 # https://github.com/rcaloras/bash-preexec