diff --git a/bin/tests/system/isctest/instance.py b/bin/tests/system/isctest/instance.py
index ac0fceec01..fdac94c7d2 100644
--- a/bin/tests/system/isctest/instance.py
+++ b/bin/tests/system/isctest/instance.py
@@ -142,6 +142,15 @@ class NamedInstance:
         """
         return WatchLogFromHere(self._log_file)
 
+    def reconfigure(self) -> None:
+        """
+        Reconfigure this named `instance` and wait until reconfiguration is
+        finished.  Raise an `RNDCException` if reconfiguration fails.
+        """
+        with self.watch_log_from_here() as watcher:
+            self.rndc("reconfig")
+            watcher.wait_for_line("any newly configured zones are now loaded")
+
     def _rndc_log(self, command: str, response: str) -> None:
         """
         Log an `rndc` invocation (and its output) to the `rndc.log` file in the