diff --git a/src/core.c b/src/core.c
index 8c305ea4..d9e7f7b9 100644
--- a/src/core.c
+++ b/src/core.c
@@ -14273,16 +14273,18 @@ again:
 }
 
 void mdbx_cursor_close(MDBX_cursor *mc) {
-  if (mc) {
+  if (likely(mc)) {
     mdbx_ensure(NULL, mc->mc_signature == MDBX_MC_LIVE ||
                           mc->mc_signature == MDBX_MC_READY4CLOSE);
+    MDBX_txn *const txn = mc->mc_txn;
     if (!mc->mc_backup) {
+      mc->mc_txn = NULL;
       /* Remove from txn, if tracked.
        * A read-only txn (!C_UNTRACK) may have been freed already,
        * so do not peek inside it.  Only write txns track cursors. */
       if (mc->mc_flags & C_UNTRACK) {
-        mdbx_cassert(mc, !(mc->mc_txn->mt_flags & MDBX_TXN_RDONLY));
-        MDBX_cursor **prev = &mc->mc_txn->tw.cursors[mc->mc_dbi];
+        mdbx_ensure(txn->mt_env, check_txn_rw(txn, 0) == MDBX_SUCCESS);
+        MDBX_cursor **prev = &txn->tw.cursors[mc->mc_dbi];
         while (*prev && *prev != mc)
           prev = &(*prev)->mc_next;
         mdbx_cassert(mc, *prev == mc);
@@ -14294,6 +14296,7 @@ void mdbx_cursor_close(MDBX_cursor *mc) {
     } else {
       /* Cursor closed before nested txn ends */
       mdbx_cassert(mc, mc->mc_signature == MDBX_MC_LIVE);
+      mdbx_ensure(txn->mt_env, check_txn_rw(txn, 0) == MDBX_SUCCESS);
       mc->mc_signature = MDBX_MC_WAIT4EOT;
     }
   }