diff --git a/postfix/tasks/main.yml b/postfix/tasks/main.yml
index 714787d6..6272be33 100644
--- a/postfix/tasks/main.yml
+++ b/postfix/tasks/main.yml
@@ -1,6 +1,6 @@
 ---
 - name: check if main.cf is default
-  shell: grep -v -E "^(myhostname|mydestination|mailbox_command)" /etc/postfix/main.cf  | md5sum -
+  shell: 'grep -v -E "^(myhostname|mydestination|mailbox_command)" /etc/postfix/main.cf  | md5sum -'
   changed_when: False
   check_mode: no
   register: default_main_cf