diff --git a/src/pywinctl/_pywinctl_macos.py b/src/pywinctl/_pywinctl_macos.py
index 4256ab8..4286ebf 100644
--- a/src/pywinctl/_pywinctl_macos.py
+++ b/src/pywinctl/_pywinctl_macos.py
@@ -1299,7 +1299,8 @@ def isAlive(self) -> bool:
                         set isDone to false
                         try
                             tell application "System Events" to tell application "%s"
-                                tell window winName to set prevIndex to index
+                                tell window winName
+                                end tell
                                 set isDone to true
                             end tell
                         end try