--- old/src/hotspot/share/opto/macroArrayCopy.cpp	2019-05-28 15:10:35.000000000 +0200
+++ new/src/hotspot/share/opto/macroArrayCopy.cpp	2019-05-28 15:10:29.000000000 +0200
@@ -1282,11 +1282,27 @@
   if (top_src != NULL && top_src->klass() != NULL) {
     src_elem = top_src->klass()->as_array_klass()->element_type()->basic_type();
   }
-  if (src_elem == T_ARRAY || (src_elem == T_VALUETYPE && top_src->klass()->is_obj_array_klass())) {
+  if (src_elem == T_ARRAY) {
     src_elem = T_OBJECT;
+  } else if (src_elem == T_VALUETYPE && top_src->klass()->is_obj_array_klass()) {
+    ciObjArrayKlass* array_klass = top_src->klass()->as_obj_array_klass();
+    if (top_src->klass_is_exact()) {
+      src_elem = T_OBJECT;
+    } else {
+      assert(!array_klass->storage_properties().is_null_free(), "klass should be exact");
+      src_elem = T_CONFLICT; // either flattened or not
+    }
   }
-  if (dest_elem == T_ARRAY || (dest_elem == T_VALUETYPE && top_dest->klass()->is_obj_array_klass())) {
+  if (dest_elem == T_ARRAY) {
     dest_elem = T_OBJECT;
+  } else if (dest_elem == T_VALUETYPE && top_dest->klass()->is_obj_array_klass()) {
+    ciObjArrayKlass* array_klass = top_dest->klass()->as_obj_array_klass();
+    if (top_dest->klass_is_exact()) {
+      dest_elem = T_OBJECT;
+    } else {
+      assert(!array_klass->storage_properties().is_null_free(), "klass should be exact");
+      dest_elem = T_CONFLICT; // either flattened or not
+    }
   }
 
   if (ac->is_arraycopy_validated() &&