diff --git a/src/hotspot/share/prims/jvmtiRedefineClasses.cpp b/src/hotspot/share/prims/jvmtiRedefineClasses.cpp
index 3dcb026e785..f6f194fd66f 100644
--- a/src/hotspot/share/prims/jvmtiRedefineClasses.cpp
+++ b/src/hotspot/share/prims/jvmtiRedefineClasses.cpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2003, 2023, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2003, 2024, 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
@@ -1823,6 +1823,12 @@ jvmtiError VM_RedefineClasses::merge_cp_and_rewrite(
     return JVMTI_ERROR_INTERNAL;
   }
 
+  // ensure merged constant pool size does not overflow u2
+  if (merge_cp_length > 0xFFFF) {
+    log_warning(redefine, class, constantpool)("Merged constant pool overflow: %d entries", merge_cp_length);
+    return JVMTI_ERROR_INTERNAL;
+  }
+
   // Set dynamic constants attribute from the original CP.
   if (old_cp->has_dynamic_constant()) {
     scratch_cp->set_has_dynamic_constant();