diff --git a/lib/completion.zsh b/lib/completion.zsh
index c7db2eb7b..e408d84b9 100644
--- a/lib/completion.zsh
+++ b/lib/completion.zsh
@@ -37,6 +37,9 @@ else
   zstyle ':completion:*:*:*:*:processes' command "ps -u $USER -o pid,user,comm -w -w"
 fi
 
+# auto-complete external commands
+zstyle ':completion:*' rehash true
+
 # disable named-directories autocompletion
 zstyle ':completion:*:cd:*' tag-order local-directories directory-stack path-directories