diff --git a/ext/ext_manager/main.php b/ext/ext_manager/main.php
index d4fafdc3..4d4dd645 100644
--- a/ext/ext_manager/main.php
+++ b/ext/ext_manager/main.php
@@ -188,6 +188,13 @@ class ExtManager extends Extension {
 			'define("EXTRA_EXTS", "'.implode(",", $extras).'");'."\n".
 			'?'.">"
 		);
+
+		// when the list of active extensions changes, we can be
+		// pretty sure that the list of who reacts to what will
+		// change too
+		if(file_exists("data/cache/event_listeners.php")) {
+			unlink("data/cache/event_listeners.php");
+		}
 	}
 }
 ?>