diff --git a/bin/tests/system/qmin/ans2/ans.py b/bin/tests/system/qmin/ans2/ans.py
index 7fa6a6c2c5..18f077781e 100644
--- a/bin/tests/system/qmin/ans2/ans.py
+++ b/bin/tests/system/qmin/ans2/ans.py
@@ -101,7 +101,7 @@ class StaleHandler(DomainHandler):
             yield send_delegation(qctx, b_stale, "10.53.0.4")
 
 
-if __name__ == "__main__":
+def main() -> None:
     server = AsyncDnsServer()
     server.install_response_handler(QueryLogger())
     server.install_response_handler(BadHandler())
@@ -109,3 +109,7 @@ if __name__ == "__main__":
     server.install_response_handler(SlowHandler())
     server.install_response_handler(StaleHandler())
     server.run()
+
+
+if __name__ == "__main__":
+    main()
diff --git a/bin/tests/system/qmin/ans3/ans.py b/bin/tests/system/qmin/ans3/ans.py
index 057bbb34d5..6547dd2f9b 100644
--- a/bin/tests/system/qmin/ans3/ans.py
+++ b/bin/tests/system/qmin/ans3/ans.py
@@ -37,10 +37,14 @@ class ZoopBoingSlowHandler(DelayedResponseHandler):
     delay = 0.4
 
 
-if __name__ == "__main__":
+def main() -> None:
     server = AsyncDnsServer()
     server.install_response_handler(QueryLogger())
     server.install_response_handler(ZoopBoingBadHandler())
     server.install_response_handler(ZoopBoingUglyHandler())
     server.install_response_handler(ZoopBoingSlowHandler())
     server.run()
+
+
+if __name__ == "__main__":
+    main()
diff --git a/bin/tests/system/qmin/ans4/ans.py b/bin/tests/system/qmin/ans4/ans.py
index ca43845a1d..ebe500bad6 100644
--- a/bin/tests/system/qmin/ans4/ans.py
+++ b/bin/tests/system/qmin/ans4/ans.py
@@ -83,7 +83,7 @@ class IckyPtangZoopBoingSlowHandler(DelayedResponseHandler):
     delay = 0.4
 
 
-if __name__ == "__main__":
+def main() -> None:
     server = AsyncDnsServer()
     server.install_response_handler(QueryLogger())
     server.install_response_handler(StaleHandler())
@@ -91,3 +91,7 @@ if __name__ == "__main__":
     server.install_response_handler(IckyPtangZoopBoingUglyHandler())
     server.install_response_handler(IckyPtangZoopBoingSlowHandler())
     server.run()
+
+
+if __name__ == "__main__":
+    main()
diff --git a/bin/tests/system/upforwd/ans4/ans.py b/bin/tests/system/upforwd/ans4/ans.py
index bd6e863bd7..9c5f940b5c 100644
--- a/bin/tests/system/upforwd/ans4/ans.py
+++ b/bin/tests/system/upforwd/ans4/ans.py
@@ -14,7 +14,11 @@ information regarding copyright ownership.
 from isctest.asyncserver import AsyncDnsServer, IgnoreAllQueries
 
 
-if __name__ == "__main__":
+def main() -> None:
     server = AsyncDnsServer()
     server.install_response_handler(IgnoreAllQueries())
     server.run()
+
+
+if __name__ == "__main__":
+    main()