--- a/net/minecraft/world/entity/Marker.java
+++ b/net/minecraft/world/entity/Marker.java
@@ -39,8 +39,9 @@
     }
 
     @Override
-    protected void addPassenger(Entity passenger) {
+    protected boolean addPassenger(Entity passenger) { // Paper - fix upstream
         passenger.stopRiding();
+        return false; // Paper - fix upstream
     }
 
     @Override
