diff --git a/lib/ansible/modules/cloud/amazon/route53.py b/lib/ansible/modules/cloud/amazon/route53.py
index bd80e1de7f..08f5efc701 100644
--- a/lib/ansible/modules/cloud/amazon/route53.py
+++ b/lib/ansible/modules/cloud/amazon/route53.py
@@ -499,9 +499,9 @@ def main():
         mutually_exclusive=[('failover', 'region', 'weight')],
         # failover, region and weight require identifier
         required_by=dict(
-            failover=('identifier'),
-            region=('identifier'),
-            weight=('identifier'),
+            failover=('identifier',),
+            region=('identifier',),
+            weight=('identifier',),
         ),
     )
 
diff --git a/lib/ansible/modules/system/cron.py b/lib/ansible/modules/system/cron.py
index 34148afebc..1d290a3d82 100644
--- a/lib/ansible/modules/system/cron.py
+++ b/lib/ansible/modules/system/cron.py
@@ -583,10 +583,10 @@ def main():
             ['insertafter', 'insertbefore'],
         ],
         required_by=dict(
-            cron_file=('user'),
+            cron_file=('user',),
         ),
         required_if=(
-            ('state', 'present', ('job')),
+            ('state', 'present', ('job',)),
         ),
     )
 
diff --git a/lib/ansible/modules/system/firewalld.py b/lib/ansible/modules/system/firewalld.py
index 970f158d76..21d20de8e6 100644
--- a/lib/ansible/modules/system/firewalld.py
+++ b/lib/ansible/modules/system/firewalld.py
@@ -648,8 +648,8 @@ def main():
         ),
         supports_check_mode=True,
         required_by=dict(
-            interface=('zone'),
-            source=('permanent'),
+            interface=('zone',),
+            source=('permanent',),
         ),
     )
 
diff --git a/lib/ansible/modules/system/interfaces_file.py b/lib/ansible/modules/system/interfaces_file.py
index 562f07e7e3..b856806923 100644
--- a/lib/ansible/modules/system/interfaces_file.py
+++ b/lib/ansible/modules/system/interfaces_file.py
@@ -361,7 +361,7 @@ def main():
         add_file_common_args=True,
         supports_check_mode=True,
         required_by=dict(
-            option=('iface'),
+            option=('iface',),
         ),
     )