diff --git a/src/hotspot/share/gc/z/zBarrier.cpp b/src/hotspot/share/gc/z/zBarrier.cpp
index 93700cc28da1a..36abfd7cf06b6 100644
--- a/src/hotspot/share/gc/z/zBarrier.cpp
+++ b/src/hotspot/share/gc/z/zBarrier.cpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2015, 2020, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2015, 2021, 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
@@ -22,6 +22,7 @@
  */
 
 #include "precompiled.hpp"
+#include "classfile/javaClasses.hpp"
 #include "gc/z/zBarrier.inline.hpp"
 #include "gc/z/zHeap.inline.hpp"
 #include "gc/z/zOop.inline.hpp"
@@ -239,6 +240,20 @@ oop ZBarrier::weak_load_barrier_on_phantom_oop_field_preloaded(volatile narrowOo
   return NULL;
 }
 
+#ifdef ASSERT
+
+// ON_WEAK barriers should only ever be applied to j.l.r.Reference.referents.
+void ZBarrier::verify_on_weak(volatile oop* referent_addr) {
+  if (referent_addr != NULL) {
+    uintptr_t base = (uintptr_t)referent_addr - java_lang_ref_Reference::referent_offset();
+    oop obj = cast_to_oop(base);
+    assert(oopDesc::is_oop(obj), "Verification failed for: ref " PTR_FORMAT " obj: " PTR_FORMAT, (uintptr_t)referent_addr, base);
+    assert(java_lang_ref_Reference::is_referent_field(obj, java_lang_ref_Reference::referent_offset()), "Sanity");
+  }
+}
+
+#endif
+
 void ZLoadBarrierOopClosure::do_oop(oop* p) {
   ZBarrier::load_barrier_on_oop_field(p);
 }
diff --git a/src/hotspot/share/gc/z/zBarrier.hpp b/src/hotspot/share/gc/z/zBarrier.hpp
index 48f652b3c5de4..f957872684d08 100644
--- a/src/hotspot/share/gc/z/zBarrier.hpp
+++ b/src/hotspot/share/gc/z/zBarrier.hpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2015, 2020, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2015, 2021, 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
@@ -75,6 +75,8 @@ class ZBarrier : public AllStatic {
   static uintptr_t mark_barrier_on_oop_slow_path(uintptr_t addr);
   static uintptr_t mark_barrier_on_finalizable_oop_slow_path(uintptr_t addr);
 
+  static void verify_on_weak(volatile oop* referent_addr) NOT_DEBUG_RETURN;
+
 public:
   // Load barrier
   static  oop load_barrier_on_oop(oop o);
diff --git a/src/hotspot/share/gc/z/zBarrier.inline.hpp b/src/hotspot/share/gc/z/zBarrier.inline.hpp
index 47210c92cdb05..9d6879b72d56c 100644
--- a/src/hotspot/share/gc/z/zBarrier.inline.hpp
+++ b/src/hotspot/share/gc/z/zBarrier.inline.hpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2015, 2020, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2015, 2021, 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
@@ -24,7 +24,6 @@
 #ifndef SHARE_GC_Z_ZBARRIER_INLINE_HPP
 #define SHARE_GC_Z_ZBARRIER_INLINE_HPP
 
-#include "classfile/javaClasses.hpp"
 #include "gc/z/zAddress.inline.hpp"
 #include "gc/z/zBarrier.hpp"
 #include "gc/z/zOop.inline.hpp"
@@ -242,18 +241,6 @@ inline void ZBarrier::load_barrier_on_oop_array(volatile oop* p, size_t length)
   }
 }
 
-// ON_WEAK barriers should only ever be applied to j.l.r.Reference.referents.
-inline void verify_on_weak(volatile oop* referent_addr) {
-#ifdef ASSERT
-  if (referent_addr != NULL) {
-    uintptr_t base = (uintptr_t)referent_addr - java_lang_ref_Reference::referent_offset();
-    oop obj = cast_to_oop(base);
-    assert(oopDesc::is_oop(obj), "Verification failed for: ref " PTR_FORMAT " obj: " PTR_FORMAT, (uintptr_t)referent_addr, base);
-    assert(java_lang_ref_Reference::is_referent_field(obj, java_lang_ref_Reference::referent_offset()), "Sanity");
-  }
-#endif
-}
-
 inline oop ZBarrier::load_barrier_on_weak_oop_field_preloaded(volatile oop* p, oop o) {
   verify_on_weak(p);