diff --git a/CHANGELOG.md b/CHANGELOG.md
index 26c58cd3..7f6c600d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -18,6 +18,7 @@ The **patch** part changes incrementally at each release.
 * haproxy: chroot and socket path are configurable
 * redis: create sudoers file if missing
 * redis: new syntax for match filter
+* redis: raise an error is port 6379 is used in "instance" mode
 
 ### Fixed
 
diff --git a/redis/tasks/instance-server.yml b/redis/tasks/instance-server.yml
index e87c6ce9..6437567c 100644
--- a/redis/tasks/instance-server.yml
+++ b/redis/tasks/instance-server.yml
@@ -1,5 +1,11 @@
 ---
 
+- name: Verify Redis port
+  assert:
+    that:
+      - redis_port != 6379
+    msg: "If you want to use port 6379, use the default instance, not a named instance."
+
 - name: "Instance '{{ redis_instance_name }}' group is present"
   group:
     name: "redis-{{ redis_instance_name }}"