diff a/src/hotspot/share/gc/g1/g1Allocator.hpp b/src/hotspot/share/gc/g1/g1Allocator.hpp
--- a/src/hotspot/share/gc/g1/g1Allocator.hpp
+++ b/src/hotspot/share/gc/g1/g1Allocator.hpp
@@ -1,7 +1,7 @@
 /*
- * Copyright (c) 2014, 2025, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2014, 2026, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License version 2 only, as
  * published by the Free Software Foundation.
@@ -73,10 +73,12 @@
   // Accessors to the allocation regions.
   inline MutatorAllocRegion* mutator_alloc_region(uint node_index);
   inline SurvivorGCAllocRegion* survivor_gc_alloc_region(uint node_index);
   inline OldGCAllocRegion* old_gc_alloc_region();
 
+  void assert_not_humongous(size_t word_size) NOT_DEBUG_RETURN;
+
   // Allocation attempt during GC for a survivor object / PLAB.
   HeapWord* survivor_attempt_allocation(uint node_index,
                                         size_t min_word_size,
                                         size_t desired_word_size,
                                         size_t* actual_word_size);