diff --git a/CHANGELOG.md b/CHANGELOG.md
index 5959858fb..a2e3184df 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -26,6 +26,8 @@
   * Support for unset variables without a default value is now deprecated.
     Please change all instances of `"${FOO}"` in your `settings.json` to
     `${FOO:null}` to keep the current behavior.
+  * The `DB_*` variable substitutions in `settings.json.docker` that previously
+    defaulted to `null` now default to "undefined".
 
 ### Notable enhancements
 
diff --git a/settings.json.docker b/settings.json.docker
index 426a58953..d9373f5eb 100644
--- a/settings.json.docker
+++ b/settings.json.docker
@@ -207,12 +207,12 @@
 
   "dbType": "${DB_TYPE:dirty}",
   "dbSettings": {
-    "host":     "${DB_HOST:null}",
-    "port":     "${DB_PORT:null}",
-    "database": "${DB_NAME:null}",
-    "user":     "${DB_USER:null}",
-    "password": "${DB_PASS:null}",
-    "charset":  "${DB_CHARSET:null}",
+    "host":     "${DB_HOST:undefined}",
+    "port":     "${DB_PORT:undefined}",
+    "database": "${DB_NAME:undefined}",
+    "user":     "${DB_USER:undefined}",
+    "password": "${DB_PASS:undefined}",
+    "charset":  "${DB_CHARSET:undefined}",
     "filename": "${DB_FILENAME:var/dirty.db}"
   },