diff --git a/src/main/java/world/bentobox/aoneblock/listeners/BossBarListener.java b/src/main/java/world/bentobox/aoneblock/listeners/BossBarListener.java
index e804ccf..196176f 100644
--- a/src/main/java/world/bentobox/aoneblock/listeners/BossBarListener.java
+++ b/src/main/java/world/bentobox/aoneblock/listeners/BossBarListener.java
@@ -47,6 +47,9 @@ public BossBarListener(AOneBlock addon) {
 
     @EventHandler(priority = EventPriority.NORMAL, ignoreCancelled = true)
     public void onBreakBlockEvent(MagicBlockEvent e) {
+        if (e.getPlayerUUID() == null) {
+            return;
+        }
         // Update boss bar
         tryToShowBossBar(e.getPlayerUUID(), e.getIsland());
         tryToShowActionBar(e.getPlayerUUID(), e.getIsland());
diff --git a/src/test/java/world/bentobox/aoneblock/listeners/BossBarListenerTest.java b/src/test/java/world/bentobox/aoneblock/listeners/BossBarListenerTest.java
index 599fec6..69872f4 100644
--- a/src/test/java/world/bentobox/aoneblock/listeners/BossBarListenerTest.java
+++ b/src/test/java/world/bentobox/aoneblock/listeners/BossBarListenerTest.java
@@ -211,4 +211,17 @@ void testBukkitToAdventureParsesHex() {
     void testBukkitToAdventureNullIsEmpty() {
         assertEquals(Component.empty(), BossBarListener.bukkitToAdventure(null));
     }
+
+    /**
+     * Test for https://github.com/BentoBoxWorld/AOneBlock/issues/557 - NPC/minion breaks
+     * fire MagicBlockEvent with a null playerUUID; the listener must not throw.
+     */
+    @Test
+    void testNullPlayerUUIDDoesNotThrow() {
+        when(island.isAllowed(addon.ONEBLOCK_BOSSBAR)).thenReturn(true);
+        when(island.isAllowed(addon.ONEBLOCK_ACTIONBAR)).thenReturn(true);
+        bbl.onBreakBlockEvent(new MagicBlockEvent(island, null, null, block, Material.STONE));
+        verify(mockPlayer, never()).sendActionBar(any(Component.class));
+        verify(bossBar, never()).addPlayer(any());
+    }
 }