diff --git a/src/hotspot/share/runtime/os.cpp b/src/hotspot/share/runtime/os.cpp
index f24d9573236..35dd898ff7d 100644
--- a/src/hotspot/share/runtime/os.cpp
+++ b/src/hotspot/share/runtime/os.cpp
@@ -694,7 +694,7 @@ void* os::realloc(void *memblock, size_t size, MEMFLAGS memflags, const NativeCa
 
   // Special handling for NMT preinit phase before arguments are parsed
   void* rc = nullptr;
-  if (NMTPreInit::handle_realloc(&rc, memblock, size)) {
+  if (NMTPreInit::handle_realloc(&rc, memblock, size, memflags)) {
     return rc;
   }
 
@@ -727,6 +727,8 @@ void* os::realloc(void *memblock, size_t size, MEMFLAGS memflags, const NativeCa
     // Perform integrity checks on and mark the old block as dead *before* calling the real realloc(3) since it
     // may invalidate the old block, including its header.
     MallocHeader* header = MallocHeader::resolve_checked(memblock);
+    assert(memflags == header->flags(), "weird NMT flags mismatch (new:\"%s\" != old:\"%s\")\n",
+           NMTUtil::flag_to_name(memflags), NMTUtil::flag_to_name(header->flags()));
     const MallocHeader::FreeInfo free_info = header->free_info();
     header->mark_block_as_dead();
 
diff --git a/src/hotspot/share/services/nmtPreInit.cpp b/src/hotspot/share/services/nmtPreInit.cpp
index c63aaac6cf2..ff29195b5cf 100644
--- a/src/hotspot/share/services/nmtPreInit.cpp
+++ b/src/hotspot/share/services/nmtPreInit.cpp
@@ -172,8 +172,8 @@ void NMTPreInit::create_table() {
 }
 
 // Allocate with os::malloc (hidden to prevent having to include os.hpp)
-void* NMTPreInit::do_os_malloc(size_t size) {
-  return os::malloc(size, mtNMT);
+void* NMTPreInit::do_os_malloc(size_t size, MEMFLAGS memflags) {
+  return os::malloc(size, memflags);
 }
 
 // Switches from NMT pre-init state to NMT post-init state;
diff --git a/src/hotspot/share/services/nmtPreInit.hpp b/src/hotspot/share/services/nmtPreInit.hpp
index 19e87a44679..30e67ffcbec 100644
--- a/src/hotspot/share/services/nmtPreInit.hpp
+++ b/src/hotspot/share/services/nmtPreInit.hpp
@@ -248,7 +248,7 @@ class NMTPreInit : public AllStatic {
   }
 
   // Just a wrapper for os::malloc to avoid including os.hpp here.
-  static void* do_os_malloc(size_t size);
+  static void* do_os_malloc(size_t size, MEMFLAGS memflags);
 
 public:
 
@@ -276,7 +276,7 @@ public:
   // Called from os::realloc.
   // Returns true if reallocation was handled here; in that case,
   // *rc contains the return address.
-  static bool handle_realloc(void** rc, void* old_p, size_t new_size) {
+  static bool handle_realloc(void** rc, void* old_p, size_t new_size, MEMFLAGS memflags) {
     if (old_p == nullptr) {                  // realloc(null, n)
       return handle_malloc(rc, new_size);
     }
@@ -305,7 +305,7 @@ public:
       //   and confusing us.
       const NMTPreInitAllocation* a = find_in_map(old_p);
       if (a != nullptr) { // this was originally a pre-init allocation
-        void* p_new = do_os_malloc(new_size);
+        void* p_new = do_os_malloc(new_size, memflags);
         ::memcpy(p_new, a->payload(), MIN2(a->size, new_size));
         (*rc) = p_new;
         return true;