diff --git a/actions/dynamicdns b/actions/dynamicdns
index 0e111b45b..3cbe07793 100755
--- a/actions/dynamicdns
+++ b/actions/dynamicdns
@@ -106,7 +106,10 @@ def subcommand_export_config(_):
                               and _active_config.exists()):
         enabled = True
 
-    output_config = {'enabled': enabled, 'domains': {domain['domain']: domain}}
+    output_config = {'enabled': enabled, 'domains': {}}
+    if domain['domain']:
+        output_config['domains'][domain['domain']] = domain
+
     print(json.dumps(output_config))
 
 
diff --git a/plinth/modules/dynamicdns/__init__.py b/plinth/modules/dynamicdns/__init__.py
index 9fc18467c..170f21552 100644
--- a/plinth/modules/dynamicdns/__init__.py
+++ b/plinth/modules/dynamicdns/__init__.py
@@ -258,7 +258,18 @@ def get_config():
     """Return the current configuration."""
     default_config = {'domains': {}}
     config = kvstore.get_default('dynamicdns_config', '{}')
-    return json.loads(config) or default_config
+    config = json.loads(config) or default_config
+    return _fix_corrupt_config(config)
+
+
+def _fix_corrupt_config(config):
+    """Fix malformed configuration result of bug in older version."""
+    if 'null' not in config['domains']:
+        return config
+
+    del config['domains']['null']
+    set_config(config)
+    return config
 
 
 def set_config(config):