craftbukkit/nms-patches/net/minecraft/world/item/ItemEnderEye.patch

--- a/net/minecraft/world/item/ItemEnderEye.java
+++ b/net/minecraft/world/item/ItemEnderEye.java
@@ -101,7 +101,11 @@
                 entityendersignal.setItem(itemstack);
                 entityendersignal.signalTo(blockposition);
                 world.gameEvent(GameEvent.PROJECTILE_SHOOT, entityendersignal.position(), GameEvent.a.of((Entity) entityhuman));
-                world.addFreshEntity(entityendersignal);
+                // CraftBukkit start
+                if (!world.addFreshEntity(entityendersignal)) {
+                    return EnumInteractionResult.FAIL;
+                }
+                // CraftBukkit end
                 if (entityhuman instanceof EntityPlayer) {
                     EntityPlayer entityplayer = (EntityPlayer) entityhuman;