diff --git a/Objects/obmalloc.c b/Objects/obmalloc.c
index 1485172102..359ff6583b 100644
--- a/Objects/obmalloc.c
+++ b/Objects/obmalloc.c
@@ -1460,11 +1460,13 @@ static void *
 _PyMem_DebugRawRealloc(void *ctx, void *p, size_t nbytes)
 {
     debug_alloc_api_t *api = (debug_alloc_api_t *)ctx;
-    uint8_t *q = (uint8_t *)p;
+    uint8_t *q = (uint8_t *)p, *r;
     uint8_t *tail;
     size_t total;       /* nbytes + 4*SST */
     size_t original_nbytes;
-    int i;
+#define ERASED_SIZE 8
+    /* A copy of erased bytes. */
+    uint8_t save[2*ERASED_SIZE];
 
     if (p == NULL)
         return _PyMem_DebugRawAlloc(0, ctx, nbytes);
@@ -1477,21 +1479,53 @@ _PyMem_DebugRawRealloc(void *ctx, void *p, size_t nbytes)
         /* overflow:  can't represent total as a Py_ssize_t */
         return NULL;
 
+    tail = q + original_nbytes;
+    /* Mark the header, the trailer, ERASED_SIZE bytes at the begin and
+       ERASED_SIZE bytes at the end as dead and save the copy of erased bytes.
+     */
+    if (original_nbytes <= 2*ERASED_SIZE) {
+        memcpy(save, q, original_nbytes);
+        memset(q - 2*SST, DEADBYTE, original_nbytes + 4*SST);
+    }
+    else {
+        memcpy(save, q, ERASED_SIZE);
+        memset(q - 2*SST, DEADBYTE, ERASED_SIZE + 2*SST);
+        memcpy(&save[ERASED_SIZE], tail - ERASED_SIZE, ERASED_SIZE);
+        memset(tail - ERASED_SIZE, DEADBYTE, ERASED_SIZE + 2*SST);
+    }
+
     /* Resize and add decorations. */
-    q = (uint8_t *)api->alloc.realloc(api->alloc.ctx, q - 2*SST, total);
-    if (q == NULL)
-        return NULL;
+    r = (uint8_t *)api->alloc.realloc(api->alloc.ctx, q - 2*SST, total);
+    if (r != NULL) {
+        q = r;
+    }
 
     write_size_t(q, nbytes);
-    assert(q[SST] == (uint8_t)api->api_id);
-    for (i = 1; i < SST; ++i)
-        assert(q[SST + i] == FORBIDDENBYTE);
+    q[SST] = (uint8_t)api->api_id;
+    memset(q + SST + 1, FORBIDDENBYTE, SST-1);
     q += 2*SST;
 
     tail = q + nbytes;
     memset(tail, FORBIDDENBYTE, SST);
     write_size_t(tail + SST, _PyRuntime.mem.serialno);
 
+    /* Restore saved bytes. */
+    if (original_nbytes <= 2*ERASED_SIZE) {
+        memcpy(q, save, Py_MIN(nbytes, original_nbytes));
+    }
+    else {
+        if (nbytes > original_nbytes - ERASED_SIZE) {
+            memcpy(q + original_nbytes - ERASED_SIZE, &save[ERASED_SIZE],
+                   Py_MIN(nbytes - original_nbytes + ERASED_SIZE, ERASED_SIZE));
+        }
+        memcpy(q, save, Py_MIN(nbytes, ERASED_SIZE));
+    }
+    _PyMem_DebugCheckAddress(api->api_id, q);
+
+    if (r == NULL) {
+        return NULL;
+    }
+
     if (nbytes > original_nbytes) {
         /* growing:  mark new extra memory clean */
         memset(q + original_nbytes, CLEANBYTE,