diff --git a/roles/docker/defaults/main.yml b/roles/docker/defaults/main.yml
index 196e59b4cd41c3b1886816b3063814ba91889048..70289582b2bad328a2cb2dfff6424ff49fa90389 100644
--- a/roles/docker/defaults/main.yml
+++ b/roles/docker/defaults/main.yml
@@ -1,4 +1,4 @@
-docker_version: 1.10
+docker_version: '1.10'
 
 docker_package_info:
   pkgs:
diff --git a/roles/docker/vars/debian.yml b/roles/docker/vars/debian.yml
index 192517097ae9b47dfb51c5540322de1503d6606d..964f59431d184cb975b6a84e7f032c8e2775caf8 100644
--- a/roles/docker/vars/debian.yml
+++ b/roles/docker/vars/debian.yml
@@ -2,16 +2,16 @@ docker_kernel_min_version: '3.2'
 
 # https://apt.dockerproject.org/repo/dists/debian-wheezy/main/filelist
 docker_versioned_pkg:
-  latest: docker-engine
-  1.9: docker-engine=1.9.1-0~{{ ansible_distribution_release|lower }}
-  1.10: docker-engine=1.10.3-0~{{ ansible_distribution_release|lower }}
-  1.11: docker-engine=1.11.2-0~{{ ansible_distribution_release|lower }}
-  1.12: docker-engine=1.12.1-0~{{ ansible_distribution_release|lower }}
+  'latest': docker-engine
+  '1.9': docker-engine=1.9.1-0~{{ ansible_distribution_release|lower }}
+  '1.10': docker-engine=1.10.3-0~{{ ansible_distribution_release|lower }}
+  '1.11': docker-engine=1.11.2-0~{{ ansible_distribution_release|lower }}
+  '1.12': docker-engine=1.12.1-0~{{ ansible_distribution_release|lower }}
 
 docker_package_info:
   pkg_mgr: apt
   pkgs:
-    - name: "{{ docker_versioned_pkg[docker_version] }}"
+    - name: "{{ docker_versioned_pkg[docker_version | string] }}"
       force: yes
 
 docker_repo_key_info:
diff --git a/roles/docker/vars/fedora.yml b/roles/docker/vars/fedora.yml
index 3fd06b4b3abdc98118d6934602ba5b61dd897dd8..1ed1a1338b9e0948c46e60055a1fe7a3caf3d9f2 100644
--- a/roles/docker/vars/fedora.yml
+++ b/roles/docker/vars/fedora.yml
@@ -1,16 +1,16 @@
 docker_kernel_min_version: '0'
 
 docker_versioned_pkg:
-  latest: docker
-  1.9: docker-1:1.9.1
-  1.10: docker-1:1.10.1
-  1.11: docker-1:1.11.2
-  1.12: docker-1:1.12.1
+  'latest': docker
+  '1.9': docker-1:1.9.1
+  '1.10': docker-1:1.10.1
+  '1.11': docker-1:1.11.2
+  '1.12': docker-1:1.12.1
 
 docker_package_info:
   pkg_mgr: dnf
   pkgs:
-    - name: "{{ docker_versioned_pkg[docker_version] }}"
+    - name: "{{ docker_versioned_pkg[docker_version | string] }}"
 
 docker_repo_key_info:
   pkg_key: ''
diff --git a/roles/docker/vars/ubuntu-16.04.yml b/roles/docker/vars/ubuntu-16.04.yml
index 208fe5edc7d206abf3a06c08a3802d32fb74e727..b59bbd81c18d01e9e4cdbbb35c7eaaccc01b6e2c 100644
--- a/roles/docker/vars/ubuntu-16.04.yml
+++ b/roles/docker/vars/ubuntu-16.04.yml
@@ -1,17 +1,17 @@
 ---
-docker_version: 1.11
+docker_version: '1.11'
 docker_kernel_min_version: '3.2'
 
 # https://apt.dockerproject.org/repo/dists/ubuntu-xenial/main/filelist
 docker_versioned_pkg:
-  latest: docker-engine
-  1.11: docker-engine=1.11.1-0~{{ ansible_distribution_release|lower }}
-  1.12: docker-engine=1.12.1-0~{{ ansible_distribution_release|lower }}
+  'latest': docker-engine
+  '1.11': docker-engine=1.11.1-0~{{ ansible_distribution_release|lower }}
+  '1.12': docker-engine=1.12.1-0~{{ ansible_distribution_release|lower }}
 
 docker_package_info:
   pkg_mgr: apt
   pkgs:
-    - name: "{{ docker_versioned_pkg[docker_version] }}"
+    - name: "{{ docker_versioned_pkg[docker_version | string] }}"
       force: yes
 
 docker_repo_key_info:
diff --git a/roles/docker/vars/ubuntu.yml b/roles/docker/vars/ubuntu.yml
index 1bf8a44a0444ec396b11365ff870d2b1bd97e4f8..2e73d8c2d8f39508fc1e95e2ce05afc5a24ee2d8 100644
--- a/roles/docker/vars/ubuntu.yml
+++ b/roles/docker/vars/ubuntu.yml
@@ -3,16 +3,16 @@ docker_kernel_min_version: '3.2'
 
 # https://apt.dockerproject.org/repo/dists/ubuntu-trusty/main/filelist
 docker_versioned_pkg:
-  latest: docker-engine
-  1.9: docker-engine=1.9.0-0~{{ ansible_distribution_release|lower }}
-  1.10: docker-engine=1.10.3-0~{{ ansible_distribution_release|lower }}
-  1.11: docker-engine=1.11.1-0~{{ ansible_distribution_release|lower }}
-  1.12: docker-engine=1.12.1-0~{{ ansible_distribution_release|lower }}
+  'latest': docker-engine
+  '1.9': docker-engine=1.9.0-0~{{ ansible_distribution_release|lower }}
+  '1.10': docker-engine=1.10.3-0~{{ ansible_distribution_release|lower }}
+  '1.11': docker-engine=1.11.1-0~{{ ansible_distribution_release|lower }}
+  '1.12': docker-engine=1.12.1-0~{{ ansible_distribution_release|lower }}
 
 docker_package_info:
   pkg_mgr: apt
   pkgs:
-    - name: "{{ docker_versioned_pkg[docker_version] }}"
+    - name: "{{ docker_versioned_pkg[docker_version | string] }}"
       force: yes
 
 docker_repo_key_info: