diff --git a/roles/StackStorm.mongodb/tasks/mongodb_debian.yml b/roles/StackStorm.mongodb/tasks/mongodb_debian.yml
index 328ee7ae..94b235a2 100644
--- a/roles/StackStorm.mongodb/tasks/mongodb_debian.yml
+++ b/roles/StackStorm.mongodb/tasks/mongodb_debian.yml
@@ -1,4 +1,17 @@
 ---
+# gpg is required for apt_key and may be missing in some minimal installations
+- name: apt | Install gpg
+  become: yes
+  apt:
+    name: gpg
+    state: present
+    update_cache: yes
+    cache_valid_time: 3600
+  register: _task
+  retries: 5
+  delay: 3
+  until: _task is succeeded
+
 - name: apt | Add mongodb key
   become: yes
   apt_key:
diff --git a/roles/StackStorm.st2/tasks/version.yml b/roles/StackStorm.st2/tasks/version.yml
index d62315b4..34aee92b 100644
--- a/roles/StackStorm.st2/tasks/version.yml
+++ b/roles/StackStorm.st2/tasks/version.yml
@@ -9,7 +9,7 @@
 # Injecting 'st2_services' var in the middle of play verified to work with 'restart st2' handler as handlers flushed as last step
 - name: Redefine list of services based on st2 version
   set_fact:
-    st2_services: "{{ st2_services }} + {{ item.1 }}"
+    st2_services: "{{ st2_services + item.1 }}"
   # dict2items not available until 2.6, so use Jinja's dictsort instead
   loop: "{{ st2_services_versioned | dictsort }}"
   when: item.0 is version_compare(st2_version_installed, '<=')