diff --git a/src/core.c b/src/core.c
index fec11370..eadfb491 100644
--- a/src/core.c
+++ b/src/core.c
@@ -3391,7 +3391,8 @@ static int __must_check_result cursor_last(MDBX_cursor *mc, MDBX_val *key,
 static int __must_check_result cursor_init(MDBX_cursor *mc, const MDBX_txn *txn,
                                            size_t dbi);
 static int __must_check_result cursor_xinit0(MDBX_cursor *mc);
-static int __must_check_result cursor_xinit1(MDBX_cursor *mc, MDBX_node *node,
+static int __must_check_result cursor_xinit1(MDBX_cursor *mc,
+                                             const MDBX_node *node,
                                              const MDBX_page *mp);
 static int __must_check_result cursor_xinit2(MDBX_cursor *mc,
                                              MDBX_xcursor *src_mx,
@@ -16616,39 +16617,41 @@ static int cursor_sibling(MDBX_cursor *mc, int dir) {
 /* Move the cursor to the next data item. */
 static int cursor_next(MDBX_cursor *mc, MDBX_val *key, MDBX_val *data,
                        MDBX_cursor_op op) {
-  MDBX_page *mp;
-  MDBX_node *node;
+  assert(op == MDBX_NEXT || op == MDBX_NEXT_DUP || op == MDBX_NEXT_NODUP);
   int rc;
 
   if (unlikely(mc->mc_flags & C_DEL) && op == MDBX_NEXT_DUP)
     return MDBX_NOTFOUND;
 
-  if (unlikely(!(mc->mc_flags & C_INITIALIZED)))
+  if (unlikely(!(mc->mc_flags & C_INITIALIZED))) {
+    if (unlikely(mc->mc_flags & C_SUB))
+      return MDBX_NOTFOUND;
     return cursor_first(mc, key, data);
+  }
 
-  mp = mc->mc_pg[mc->mc_top];
+  const MDBX_page *mp = mc->mc_pg[mc->mc_top];
   if (unlikely(mc->mc_flags & C_EOF)) {
     if (mc->mc_ki[mc->mc_top] + (size_t)1 >= page_numkeys(mp))
       return MDBX_NOTFOUND;
     mc->mc_flags ^= C_EOF;
   }
 
-  if (mc->mc_db->md_flags & MDBX_DUPSORT) {
-    node = page_node(mp, mc->mc_ki[mc->mc_top]);
-    if (node_flags(node) & F_DUPDATA) {
-      if (op == MDBX_NEXT || op == MDBX_NEXT_DUP) {
+  if (mc->mc_xcursor) {
+    if (op != MDBX_NEXT_NODUP) {
+      const MDBX_node *node = page_node(mp, mc->mc_ki[mc->mc_top]);
+      if (node_flags(node) & F_DUPDATA) {
         rc = cursor_next(&mc->mc_xcursor->mx_cursor, data, NULL, MDBX_NEXT);
-        if (op != MDBX_NEXT || rc != MDBX_NOTFOUND) {
-          if (likely(rc == MDBX_SUCCESS))
-            get_key_optional(node, key);
-          return rc;
+        if (likely(rc == MDBX_SUCCESS)) {
+          get_key_optional(node, key);
+          return MDBX_SUCCESS;
         }
+        if (unlikely(rc != MDBX_NOTFOUND))
+          return rc;
       }
-    } else {
-      mc->mc_xcursor->mx_cursor.mc_flags &= ~(C_INITIALIZED | C_EOF);
-      if (op == MDBX_NEXT_DUP)
+      if (op != MDBX_NEXT)
         return MDBX_NOTFOUND;
     }
+    mc->mc_xcursor->mx_cursor.mc_flags &= ~(C_INITIALIZED | C_EOF);
   }
 
   DEBUG("cursor_next: top page is %" PRIaPGNO " in cursor %p", mp->mp_pgno,
@@ -16692,7 +16695,7 @@ skip:
     return MDBX_SUCCESS;
   }
 
-  node = page_node(mp, mc->mc_ki[mc->mc_top]);
+  const MDBX_node *node = page_node(mp, mc->mc_ki[mc->mc_top]);
   if (node_flags(node) & F_DUPDATA) {
     rc = cursor_xinit1(mc, node, mp);
     if (unlikely(rc != MDBX_SUCCESS))
@@ -16713,40 +16716,41 @@ skip:
 /* Move the cursor to the previous data item. */
 static int cursor_prev(MDBX_cursor *mc, MDBX_val *key, MDBX_val *data,
                        MDBX_cursor_op op) {
-  MDBX_page *mp;
-  MDBX_node *node;
+  assert(op == MDBX_PREV || op == MDBX_PREV_DUP || op == MDBX_PREV_NODUP);
   int rc;
 
   if (unlikely(mc->mc_flags & C_DEL) && op == MDBX_PREV_DUP)
     return MDBX_NOTFOUND;
 
   if (unlikely(!(mc->mc_flags & C_INITIALIZED))) {
+    if (unlikely(mc->mc_flags & C_SUB))
+      return MDBX_NOTFOUND;
     rc = cursor_last(mc, key, data);
-    if (unlikely(rc))
+    if (unlikely(rc != MDBX_SUCCESS))
       return rc;
     mc->mc_ki[mc->mc_top]++;
   }
 
-  mp = mc->mc_pg[mc->mc_top];
-  if ((mc->mc_db->md_flags & MDBX_DUPSORT) &&
-      mc->mc_ki[mc->mc_top] < page_numkeys(mp)) {
-    node = page_node(mp, mc->mc_ki[mc->mc_top]);
-    if (node_flags(node) & F_DUPDATA) {
-      if (op == MDBX_PREV || op == MDBX_PREV_DUP) {
-        rc = cursor_prev(&mc->mc_xcursor->mx_cursor, data, NULL, MDBX_PREV);
-        if (op != MDBX_PREV || rc != MDBX_NOTFOUND) {
+  const MDBX_page *mp = mc->mc_pg[mc->mc_top];
+  if (mc->mc_xcursor) {
+    if (op != MDBX_PREV_NODUP) {
+      if (likely(mc->mc_ki[mc->mc_top] < page_numkeys(mp))) {
+        const MDBX_node *node = page_node(mp, mc->mc_ki[mc->mc_top]);
+        if (node_flags(node) & F_DUPDATA) {
+          rc = cursor_prev(&mc->mc_xcursor->mx_cursor, data, NULL, MDBX_PREV);
           if (likely(rc == MDBX_SUCCESS)) {
             get_key_optional(node, key);
             mc->mc_flags &= ~C_EOF;
+            return MDBX_SUCCESS;
           }
-          return rc;
+          if (unlikely(rc != MDBX_NOTFOUND))
+            return rc;
         }
       }
-    } else {
-      mc->mc_xcursor->mx_cursor.mc_flags &= ~(C_INITIALIZED | C_EOF);
-      if (op == MDBX_PREV_DUP)
+      if (op != MDBX_PREV)
         return MDBX_NOTFOUND;
     }
+    mc->mc_xcursor->mx_cursor.mc_flags &= ~(C_INITIALIZED | C_EOF);
   }
 
   DEBUG("cursor_prev: top page is %" PRIaPGNO " in cursor %p", mp->mp_pgno,
@@ -16782,8 +16786,7 @@ static int cursor_prev(MDBX_cursor *mc, MDBX_val *key, MDBX_val *data,
     return MDBX_SUCCESS;
   }
 
-  node = page_node(mp, mc->mc_ki[mc->mc_top]);
-
+  const MDBX_node *node = page_node(mp, mc->mc_ki[mc->mc_top]);
   if (node_flags(node) & F_DUPDATA) {
     rc = cursor_xinit1(mc, node, mp);
     if (unlikely(rc != MDBX_SUCCESS))
@@ -17234,6 +17237,8 @@ static __hot int cursor_get(MDBX_cursor *mc, MDBX_val *key, MDBX_val *data,
               return rc;
           }
         } else {
+          cASSERT(mc, !mc->mc_xcursor || !(mc->mc_xcursor->mx_cursor.mc_flags &
+                                           C_INITIALIZED));
           rc = node_read(mc, node, data, mp);
           if (unlikely(rc))
             return rc;
@@ -19025,7 +19030,7 @@ static int cursor_xinit0(MDBX_cursor *mc) {
  * [in] mc The main cursor whose sorted-dups cursor is to be initialized.
  * [in] node The data containing the MDBX_db record for the sorted-dup database.
  */
-static int cursor_xinit1(MDBX_cursor *mc, MDBX_node *node,
+static int cursor_xinit1(MDBX_cursor *mc, const MDBX_node *node,
                          const MDBX_page *mp) {
   MDBX_xcursor *mx = mc->mc_xcursor;
   if (!MDBX_DISABLE_VALIDATION && unlikely(mx == nullptr)) {