diff --git a/src/mdbx.c b/src/mdbx.c
index a85ec847..1339d80c 100644
--- a/src/mdbx.c
+++ b/src/mdbx.c
@@ -9775,6 +9775,8 @@ static int mdbx_page_merge(MDBX_cursor *csrc, MDBX_cursor *cdst) {
   MDBX_val key;
   int rc;
 
+  mdbx_cassert(csrc, csrc != cdst);
+
   /* Mark dst as dirty. */
   if (unlikely(rc = mdbx_page_touch(cdst)))
     return rc;
@@ -9786,13 +9788,20 @@ static int mdbx_page_merge(MDBX_cursor *csrc, MDBX_cursor *cdst) {
              pdst->mp_pgno);
 
   mdbx_cassert(csrc, PAGETYPE(psrc) == PAGETYPE(pdst));
+  mdbx_cassert(csrc,
+               csrc->mc_dbi == cdst->mc_dbi && csrc->mc_db == cdst->mc_db);
   mdbx_cassert(csrc, csrc->mc_snum > 1); /* can't merge root page */
   mdbx_cassert(cdst, cdst->mc_snum > 1);
+  mdbx_cassert(cdst, cdst->mc_snum < cdst->mc_db->md_depth ||
+                         IS_LEAF(cdst->mc_pg[cdst->mc_db->md_depth - 1]));
+  mdbx_cassert(csrc, csrc->mc_snum < csrc->mc_db->md_depth ||
+                         IS_LEAF(csrc->mc_pg[csrc->mc_db->md_depth - 1]));
+  const int pagetype = PAGETYPE(psrc);
 
   /* Move all nodes from src to dst */
   const unsigned nkeys = NUMKEYS(pdst);
   unsigned j = nkeys;
-  if (IS_LEAF2(psrc)) {
+  if (unlikely(pagetype & P_LEAF2)) {
     key.iov_len = csrc->mc_db->md_xsize;
     key.iov_base = PAGEDATA(psrc);
     for (unsigned i = 0; i < NUMKEYS(psrc); i++, j++) {
@@ -9804,7 +9813,7 @@ static int mdbx_page_merge(MDBX_cursor *csrc, MDBX_cursor *cdst) {
   } else {
     for (unsigned i = 0; i < NUMKEYS(psrc); i++, j++) {
       srcnode = NODEPTR(psrc, i);
-      if (i == 0 && IS_BRANCH(psrc)) {
+      if (i == 0 && (pagetype & P_BRANCH)) {
         MDBX_cursor mn;
         mdbx_cursor_copy(csrc, &mn);
         mn.mc_xcursor = NULL;
@@ -9825,7 +9834,7 @@ static int mdbx_page_merge(MDBX_cursor *csrc, MDBX_cursor *cdst) {
         key.iov_base = NODEKEY(srcnode);
       }
 
-      if (IS_LEAF(psrc)) {
+      if (pagetype & P_LEAF) {
         MDBX_val data;
         data.iov_len = NODEDSZ(srcnode);
         data.iov_base = NODEDATA(srcnode);
@@ -9841,7 +9850,7 @@ static int mdbx_page_merge(MDBX_cursor *csrc, MDBX_cursor *cdst) {
 
   mdbx_debug("dst page %" PRIaPGNO " now has %u keys (%.1f%% filled)",
              pdst->mp_pgno, NUMKEYS(pdst),
-             (float)PAGEFILL(cdst->mc_txn->mt_env, pdst) / 10);
+             PAGEFILL(cdst->mc_txn->mt_env, pdst) / 10.24);
 
   mdbx_cassert(csrc, psrc == csrc->mc_pg[csrc->mc_top]);
   mdbx_cassert(cdst, pdst == cdst->mc_pg[cdst->mc_top]);
@@ -9859,26 +9868,18 @@ static int mdbx_page_merge(MDBX_cursor *csrc, MDBX_cursor *cdst) {
   }
   csrc->mc_top++;
 
-  /* If not operating on FreeDB, allow this page to be reused
-   * in this txn. Otherwise just add to free list. */
-  rc = mdbx_page_loose(csrc, psrc);
-  if (unlikely(rc))
-    return rc;
+  mdbx_cassert(csrc, psrc == csrc->mc_pg[csrc->mc_top]);
+  mdbx_cassert(cdst, pdst == cdst->mc_pg[cdst->mc_top]);
 
   {
     /* Adjust other cursors pointing to mp */
     MDBX_cursor *m2, *m3;
     const MDBX_dbi dbi = csrc->mc_dbi;
-    unsigned top = csrc->mc_top;
+    const unsigned top = csrc->mc_top;
 
     for (m2 = csrc->mc_txn->mt_cursors[dbi]; m2; m2 = m2->mc_next) {
-      if (csrc->mc_flags & C_SUB)
-        m3 = &m2->mc_xcursor->mx_cursor;
-      else
-        m3 = m2;
-      if (m3 == csrc)
-        continue;
-      if (m3->mc_snum < csrc->mc_snum)
+      m3 = (csrc->mc_flags & C_SUB) ? &m2->mc_xcursor->mx_cursor : m2;
+      if (m3 == csrc || top >= m3->mc_snum)
         continue;
       if (m3->mc_pg[top] == psrc) {
         m3->mc_pg[top] = pdst;
@@ -9893,23 +9894,94 @@ static int mdbx_page_merge(MDBX_cursor *csrc, MDBX_cursor *cdst) {
         XCURSOR_REFRESH(m3, m3->mc_pg[top], m3->mc_ki[top]);
     }
   }
-  {
-    unsigned snum = cdst->mc_snum;
-    uint16_t depth = cdst->mc_db->md_depth;
-    mdbx_cursor_pop(cdst);
-    rc = mdbx_rebalance(cdst);
-    if (unlikely(rc))
-      return rc;
-    mdbx_cassert(cdst, cdst->mc_db->md_entries > 0);
 
-    /* Did the tree height change? */
-    if (depth != cdst->mc_db->md_depth)
-      snum += cdst->mc_db->md_depth - depth;
-    mdbx_cassert(cdst, snum >= 1 && snum <= UINT16_MAX);
-    cdst->mc_snum = (uint16_t)snum;
-    cdst->mc_top = (uint16_t)(snum - 1);
+  /* If not operating on FreeDB, allow this page to be reused
+   * in this txn. Otherwise just add to free list. */
+  rc = mdbx_page_loose(csrc, psrc);
+  if (unlikely(rc))
+    return rc;
+
+  mdbx_cassert(cdst, cdst->mc_db->md_entries > 0);
+  mdbx_cassert(cdst, cdst->mc_snum <= cdst->mc_db->md_depth);
+  mdbx_cassert(cdst, cdst->mc_top > 0);
+  mdbx_cassert(cdst, cdst->mc_snum == cdst->mc_top + 1);
+  MDBX_page *const top_page = cdst->mc_pg[cdst->mc_top];
+  const indx_t top_indx = cdst->mc_ki[cdst->mc_top];
+  const uint16_t save_snum = cdst->mc_snum;
+  const uint16_t save_depth = cdst->mc_db->md_depth;
+  mdbx_cursor_pop(cdst);
+  rc = mdbx_rebalance(cdst);
+  if (unlikely(rc))
+    return rc;
+
+  mdbx_cassert(cdst, cdst->mc_db->md_entries > 0);
+  mdbx_cassert(cdst, cdst->mc_snum <= cdst->mc_db->md_depth);
+  mdbx_cassert(cdst, cdst->mc_top >= 0);
+  mdbx_cassert(cdst, cdst->mc_snum == cdst->mc_top + 1);
+
+  if (IS_LEAF(cdst->mc_pg[cdst->mc_top])) {
+    /* LY: don't touch cursor if top-page is a LEAF */
+    mdbx_cassert(cdst, IS_LEAF(cdst->mc_pg[cdst->mc_top]) ||
+                           PAGETYPE(cdst->mc_pg[cdst->mc_top]) == pagetype);
+    return MDBX_SUCCESS;
   }
-  return MDBX_SUCCESS;
+
+  if (pagetype != PAGETYPE(top_page)) {
+    /* LY: LEAF-page becomes BRANCH, unable restore cursor's stack */
+    goto bailout;
+  }
+
+  if (top_page == cdst->mc_pg[cdst->mc_top]) {
+    /* LY: don't touch cursor if prev top-page already on the top */
+    mdbx_cassert(cdst, cdst->mc_ki[cdst->mc_top] == top_indx);
+    mdbx_cassert(cdst, IS_LEAF(cdst->mc_pg[cdst->mc_top]) ||
+                           PAGETYPE(cdst->mc_pg[cdst->mc_top]) == pagetype);
+    return MDBX_SUCCESS;
+  }
+
+  const int new_snum = save_snum - save_depth + cdst->mc_db->md_depth;
+  if (unlikely(new_snum < 1 || new_snum > cdst->mc_db->md_depth)) {
+    /* LY: out of range, unable restore cursor's stack */
+    goto bailout;
+  }
+
+  if (top_page == cdst->mc_pg[new_snum - 1]) {
+    mdbx_cassert(cdst, cdst->mc_ki[new_snum - 1] == top_indx);
+    /* LY: restore cursor stack */
+    cdst->mc_snum = (uint16_t)new_snum;
+    cdst->mc_top = (uint16_t)new_snum - 1;
+    mdbx_cassert(cdst, cdst->mc_snum < cdst->mc_db->md_depth ||
+                           IS_LEAF(cdst->mc_pg[cdst->mc_db->md_depth - 1]));
+    mdbx_cassert(cdst, IS_LEAF(cdst->mc_pg[cdst->mc_top]) ||
+                           PAGETYPE(cdst->mc_pg[cdst->mc_top]) == pagetype);
+    return MDBX_SUCCESS;
+  }
+
+  MDBX_page *const stub_page = (MDBX_page *)(~(uintptr_t)top_page);
+  const indx_t stub_indx = top_indx;
+  if (save_depth > cdst->mc_db->md_depth &&
+      ((cdst->mc_pg[save_snum - 1] == top_page &&
+        cdst->mc_ki[save_snum - 1] == top_indx) ||
+       (cdst->mc_pg[save_snum - 1] == stub_page &&
+        cdst->mc_ki[save_snum - 1] == stub_indx))) {
+    /* LY: restore cursor stack */
+    cdst->mc_pg[new_snum - 1] = top_page;
+    cdst->mc_ki[new_snum - 1] = top_indx;
+    cdst->mc_pg[new_snum] = (MDBX_page *)(~(uintptr_t)cdst->mc_pg[new_snum]);
+    cdst->mc_ki[new_snum] = ~cdst->mc_ki[new_snum];
+    cdst->mc_snum = (uint16_t)new_snum;
+    cdst->mc_top = (uint16_t)new_snum - 1;
+    mdbx_cassert(cdst, cdst->mc_snum < cdst->mc_db->md_depth ||
+                           IS_LEAF(cdst->mc_pg[cdst->mc_db->md_depth - 1]));
+    mdbx_cassert(cdst, IS_LEAF(cdst->mc_pg[cdst->mc_top]) ||
+                           PAGETYPE(cdst->mc_pg[cdst->mc_top]) == pagetype);
+    return MDBX_SUCCESS;
+  }
+
+bailout:
+  /* LY: unable restore cursor's stack */
+  cdst->mc_flags &= ~C_INITIALIZED;
+  return MDBX_CURSOR_FULL;
 }
 
 /* Copy the contents of a cursor.