diff --git a/include/nuttx/mm/mm.h b/include/nuttx/mm/mm.h
index 265f92c9867..3e440947908 100644
--- a/include/nuttx/mm/mm.h
+++ b/include/nuttx/mm/mm.h
@@ -139,6 +139,10 @@
 #define MM_DUMP_LEAK(dump, pid) \
     ((dump) == PID_MM_LEAK && (pid) >= 0 && nxsched_get_tcb(pid) == NULL)
 
+#define MM_INIT_MAGIC    0xcc
+#define MM_ALLOC_MAGIC   0xaa
+#define MM_FREE_MAGIC    0x55
+
 /****************************************************************************
  * Public Types
  ****************************************************************************/
diff --git a/mm/Kconfig b/mm/Kconfig
index f53501cff3b..37e5a4f2551 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -322,8 +322,10 @@ config MM_FILL_ALLOCATIONS
 	bool "Fill allocations with debug value"
 	default n
 	---help---
-		Fill all malloc() allocations with 0xAA. This helps
-		detecting uninitialized variable errors.
+		Fill all malloc() allocations with MM_ALLOC_MAGIC.
+		Fill all add_addregion() with MM_INIT_MAGIC.
+		Fill all free() with MM_FREE_MAGIC.
+		This helps detecting uninitialized variable errors.
 
 config MM_BACKTRACE
 	int "The depth of backtrace"
diff --git a/mm/mempool/mempool.c b/mm/mempool/mempool.c
index 206c835583d..46f278e373d 100644
--- a/mm/mempool/mempool.c
+++ b/mm/mempool/mempool.c
@@ -274,7 +274,7 @@ retry:
     }
 
 #ifdef CONFIG_MM_FILL_ALLOCATIONS
-  memset(blk, 0xaa, pool->blocksize);
+  memset(blk, MM_ALLOC_MAGIC, pool->blocksize);
 #endif
 
 #if CONFIG_MM_BACKTRACE >= 0
@@ -317,7 +317,7 @@ void mempool_free(FAR struct mempool_s *pool, FAR void *blk)
 #endif
 
 #ifdef CONFIG_MM_FILL_ALLOCATIONS
-  memset(blk, 0x55, pool->blocksize);
+  memset(blk, MM_FREE_MAGIC, pool->blocksize);
 #endif
 
   if (pool->interruptsize > blocksize)
diff --git a/mm/mm_heap/mm_free.c b/mm/mm_heap/mm_free.c
index d29f901e846..39e869d8596 100644
--- a/mm/mm_heap/mm_free.c
+++ b/mm/mm_heap/mm_free.c
@@ -90,7 +90,7 @@ void mm_delayfree(FAR struct mm_heap_s *heap, FAR void *mem, bool delay)
     }
 
 #ifdef CONFIG_MM_FILL_ALLOCATIONS
-  memset(mem, 0x55, mm_malloc_size(heap, mem));
+  memset(mem, MM_FREE_MAGIC, mm_malloc_size(heap, mem));
 #endif
 
   kasan_poison(mem, mm_malloc_size(heap, mem));
diff --git a/mm/mm_heap/mm_initialize.c b/mm/mm_heap/mm_initialize.c
index 676f1901f42..31c44d64ef8 100644
--- a/mm/mm_heap/mm_initialize.c
+++ b/mm/mm_heap/mm_initialize.c
@@ -129,6 +129,12 @@ void mm_addregion(FAR struct mm_heap_s *heap, FAR void *heapstart,
   DEBUGASSERT(heapsize <= MMSIZE_MAX + 1);
 #endif
 
+#ifdef CONFIG_MM_FILL_ALLOCATIONS
+  /* Use the fill value to mark uninitialized user memory */
+
+  memset(heapstart, MM_INIT_MAGIC, heapsize);
+#endif
+
   /* Register to KASan for access check */
 
   kasan_register(heapstart, &heapsize);
diff --git a/mm/mm_heap/mm_malloc.c b/mm/mm_heap/mm_malloc.c
index 30e307f5778..68e919a3118 100644
--- a/mm/mm_heap/mm_malloc.c
+++ b/mm/mm_heap/mm_malloc.c
@@ -305,7 +305,7 @@ FAR void *mm_malloc(FAR struct mm_heap_s *heap, size_t size)
       MM_ADD_BACKTRACE(heap, node);
       kasan_unpoison(ret, mm_malloc_size(heap, ret));
 #ifdef CONFIG_MM_FILL_ALLOCATIONS
-      memset(ret, 0xaa, alignsize - MM_ALLOCNODE_OVERHEAD);
+      memset(ret, MM_ALLOC_MAGIC, alignsize - MM_ALLOCNODE_OVERHEAD);
 #endif
 #ifdef CONFIG_DEBUG_MM
       minfo("Allocated %p, size %zu\n", ret, alignsize);
diff --git a/mm/tlsf/mm_tlsf.c b/mm/tlsf/mm_tlsf.c
index ad7801f670e..0fc627ab17e 100644
--- a/mm/tlsf/mm_tlsf.c
+++ b/mm/tlsf/mm_tlsf.c
@@ -503,7 +503,7 @@ static void mm_delayfree(FAR struct mm_heap_s *heap, FAR void *mem,
   if (mm_lock(heap) == 0)
     {
 #ifdef CONFIG_MM_FILL_ALLOCATIONS
-      memset(mem, 0x55, mm_malloc_size(heap, mem));
+      memset(mem, MM_FREE_MAGIC, mm_malloc_size(heap, mem));
 #endif
 
       kasan_poison(mem, mm_malloc_size(heap, mem));
@@ -575,6 +575,12 @@ void mm_addregion(FAR struct mm_heap_s *heap, FAR void *heapstart,
 #  define idx 0
 #endif
 
+#ifdef CONFIG_MM_FILL_ALLOCATIONS
+  /* Use the fill value to mark uninitialized user memory */
+
+  memset(heapstart, 0xcc, heapsize);
+#endif
+
   /* Register to KASan for access check */
 
   kasan_register(heapstart, &heapsize);
@@ -1144,7 +1150,7 @@ FAR void *mm_malloc(FAR struct mm_heap_s *heap, size_t size)
       kasan_unpoison(ret, mm_malloc_size(heap, ret));
 
 #ifdef CONFIG_MM_FILL_ALLOCATIONS
-      memset(ret, 0xaa, mm_malloc_size(heap, ret));
+      memset(ret, 0xaa, nodesize);
 #endif
     }