diff --git a/themes/agnoster.zsh-theme b/themes/agnoster.zsh-theme
index e1a294ee8..06e7977ba 100644
--- a/themes/agnoster.zsh-theme
+++ b/themes/agnoster.zsh-theme
@@ -128,6 +128,7 @@ prompt_git() {
 }
 
 prompt_bzr() {
+    (( $+commands[bzr] )) || return
     if (bzr status >/dev/null 2>&1); then
         status_mod=`bzr status | head -n1 | grep "modified" | wc -m`
         status_all=`bzr status | head -n1 | wc -m`