diff a/src/hotspot/share/gc/shenandoah/shenandoahController.cpp b/src/hotspot/share/gc/shenandoah/shenandoahController.cpp
--- a/src/hotspot/share/gc/shenandoah/shenandoahController.cpp
+++ b/src/hotspot/share/gc/shenandoah/shenandoahController.cpp
@@ -39,11 +39,15 @@
 }
 
 void ShenandoahController::handle_alloc_failure(const ShenandoahAllocRequest& req, bool block) {
   assert(current()->is_Java_thread(), "expect Java thread here");
 
-  const bool is_humongous = ShenandoahHeapRegion::requires_humongous(req.size());
+  // Classify the failure consistently with how ShenandoahFreeSet::allocate would
+  // route this request: a fresh mutator object (_alloc_shared) may expand for an
+  // identity hash-code, every other request carries an already-final size.
+  const bool may_expand_for_hash = (req.type() == ShenandoahAllocRequest::_alloc_shared);
+  const bool is_humongous = ShenandoahHeapRegion::requires_humongous(req.size(), may_expand_for_hash);
   const GCCause::Cause cause = is_humongous ? GCCause::_shenandoah_humongous_allocation_failure : GCCause::_allocation_failure;
 
   ShenandoahHeap* const heap = ShenandoahHeap::heap();
   size_t req_byte = req.size() * HeapWordSize;
   if (heap->cancel_gc(cause)) {
@@ -61,11 +65,11 @@
 }
 
 void ShenandoahController::handle_alloc_failure_evac(size_t words) {
 
   ShenandoahHeap* const heap = ShenandoahHeap::heap();
-  const bool is_humongous = ShenandoahHeapRegion::requires_humongous(words);
+  const bool is_humongous = ShenandoahHeapRegion::requires_humongous(words, false /* may_expand_for_hash */);
   const GCCause::Cause cause = is_humongous ? GCCause::_shenandoah_humongous_allocation_failure : GCCause::_shenandoah_allocation_failure_evac;
 
   if (heap->cancel_gc(cause)) {
     log_info(gc)("Failed to allocate " PROPERFMT " for evacuation", PROPERFMTARGS(words * HeapWordSize));
   }