diff --git a/libraries/liblmdb/mdb.c b/libraries/liblmdb/mdb.c
index 0b69f43fa6..56042178e3 100644
--- a/libraries/liblmdb/mdb.c
+++ b/libraries/liblmdb/mdb.c
@@ -137,6 +137,7 @@ static NtCloseFunc *NtClose;
 #include <stdlib.h>
 #include <string.h>
 #include <time.h>
+#include <stdatomic.h>
 
 #ifdef _MSC_VER
 #include <io.h>
@@ -1302,6 +1303,8 @@ struct MDB_txn {
 	MDB_txn		*mt_parent;		/**< parent of a nested txn */
 	/** Nested txn under this txn, set together with flag #MDB_TXN_HAS_CHILD */
 	MDB_txn		*mt_child;
+	/** The count of nested RDONLY txns under this txn also named child txns */
+	atomic_uint	mt_rdonly_child_count;
 	pgno_t		mt_next_pgno;	/**< next unallocated page */
 #ifdef MDB_VL32
 	pgno_t		mt_last_pgno;	/**< last written page */
@@ -3144,6 +3147,7 @@ mdb_txn_renew0(MDB_txn *txn)
 			mdb_debug = MDB_DBG_INFO;
 #endif
 		txn->mt_child = NULL;
+		txn->mt_rdonly_child_count = 0;
 		txn->mt_loose_pgs = NULL;
 		txn->mt_loose_count = 0;
 		txn->mt_dirty_room = MDB_IDL_UM_MAX;
@@ -3220,9 +3224,15 @@ mdb_txn_begin(MDB_env *env, MDB_txn *parent, unsigned int flags, MDB_txn **ret)
 		return EACCES;
 
 	if (parent) {
-		/* Nested transactions: Max 1 child, write txns only, no writemap */
+		/* Nested transactions:
+		 * If RDONLY: Any number of children, writemap allowed
+		 * If write: Max 1 child, no writemap
+		 */
 		flags |= parent->mt_flags;
-		if (flags & (MDB_RDONLY|MDB_WRITEMAP|MDB_TXN_BLOCKED)) {
+		if (parent->mt_child && F_ISSET(parent->mt_child->mt_flags, MDB_RDONLY) && F_ISSET(flags, MDB_RDONLY)) {
+			flags &= ~MDB_TXN_HAS_CHILD;
+		}
+		if ((F_ISSET(flags, MDB_WRITEMAP) && !F_ISSET(flags, MDB_RDONLY)) || F_ISSET(flags, MDB_TXN_BLOCKED)) {
 			return (parent->mt_flags & MDB_TXN_RDONLY) ? EINVAL : MDB_BAD_TXN;
 		}
 		/* Child txns save MDB_pgstate and use own copy of cursors */
@@ -3263,6 +3273,7 @@ mdb_txn_begin(MDB_env *env, MDB_txn *parent, unsigned int flags, MDB_txn **ret)
 		unsigned int i;
 		txn->mt_cursors = (MDB_cursor **)(txn->mt_dbs + env->me_maxdbs);
 		txn->mt_dbiseqs = parent->mt_dbiseqs;
+		/* Not useful when nested RDONLY but correctly freed in mdb_txn_end */
 		txn->mt_u.dirty_list = malloc(sizeof(MDB_ID2)*MDB_IDL_UM_SIZE);
 		if (!txn->mt_u.dirty_list ||
 			!(txn->mt_free_pgs = mdb_midl_alloc(MDB_IDL_UM_MAX)))
@@ -3278,6 +3289,11 @@ mdb_txn_begin(MDB_env *env, MDB_txn *parent, unsigned int flags, MDB_txn **ret)
 		txn->mt_next_pgno = parent->mt_next_pgno;
 		parent->mt_flags |= MDB_TXN_HAS_CHILD;
 		parent->mt_child = txn;
+		if (flags & MDB_RDONLY) {
+			atomic_fetch_add(&parent->mt_rdonly_child_count, 1);
+		} else {
+			parent->mt_rdonly_child_count = 0;
+		}
 		txn->mt_parent = parent;
 		txn->mt_numdbs = parent->mt_numdbs;
 #ifdef MDB_VL32
@@ -3290,7 +3306,8 @@ mdb_txn_begin(MDB_env *env, MDB_txn *parent, unsigned int flags, MDB_txn **ret)
 		rc = 0;
 		ntxn = (MDB_ntxn *)txn;
 		ntxn->mnt_pgstate = env->me_pgstate; /* save parent me_pghead & co */
-		if (env->me_pghead) {
+		/* Do not copy parent me_pghead when nested and RDONLY */
+		if (!(flags & MDB_RDONLY) && env->me_pghead) {
 			size = MDB_IDL_SIZEOF(env->me_pghead);
 			env->me_pghead = mdb_midl_alloc(env->me_pghead[0]);
 			if (env->me_pghead)
@@ -3377,6 +3394,7 @@ static void
 mdb_txn_end(MDB_txn *txn, unsigned mode)
 {
 	MDB_env	*env = txn->mt_env;
+	unsigned int flags = txn->mt_flags;
 #if MDB_DEBUG
 	static const char *const names[] = MDB_END_NAMES;
 #endif
@@ -3389,7 +3407,7 @@ mdb_txn_end(MDB_txn *txn, unsigned mode)
 		txn->mt_txnid, (txn->mt_flags & MDB_TXN_RDONLY) ? 'r' : 'w',
 		(void *) txn, (void *)env, txn->mt_dbs[MAIN_DBI].md_root));
 
-	if (F_ISSET(txn->mt_flags, MDB_TXN_RDONLY)) {
+	if (!txn->mt_parent && F_ISSET(txn->mt_flags, MDB_TXN_RDONLY)) {
 		if (txn->mt_u.reader) {
 			txn->mt_u.reader->mr_txnid = (txnid_t)-1;
 			if (!(env->me_flags & MDB_NOTLS)) {
@@ -3413,6 +3431,7 @@ mdb_txn_end(MDB_txn *txn, unsigned mode)
 
 		txn->mt_numdbs = 0;
 		txn->mt_flags = MDB_TXN_FINISHED;
+		mdb_midl_free(txn->mt_spill_pgs);
 
 		if (!txn->mt_parent) {
 			mdb_midl_shrink(&txn->mt_free_pgs);
@@ -3428,15 +3447,19 @@ mdb_txn_end(MDB_txn *txn, unsigned mode)
 			if (env->me_txns)
 				UNLOCK_MUTEX(env->me_wmutex);
 		} else {
-			txn->mt_parent->mt_child = NULL;
-			txn->mt_parent->mt_flags &= ~MDB_TXN_HAS_CHILD;
-			env->me_pgstate = ((MDB_ntxn *)txn)->mnt_pgstate;
+			if (!F_ISSET(flags, MDB_RDONLY) || atomic_fetch_sub(&txn->mt_parent->mt_rdonly_child_count, 1) == 1) {
+				txn->mt_parent->mt_child = NULL;
+				txn->mt_parent->mt_flags &= ~MDB_TXN_HAS_CHILD;
+				env->me_pgstate = ((MDB_ntxn *)txn)->mnt_pgstate;
+			}
 			mdb_midl_free(txn->mt_free_pgs);
 			free(txn->mt_u.dirty_list);
 		}
-		mdb_midl_free(txn->mt_spill_pgs);
 
-		mdb_midl_free(pghead);
+		/* A parent and RDONLY, it's a multi-nested RDONLY transaction case */
+		if (!(txn->mt_parent && flags & MDB_RDONLY)) {
+			mdb_midl_free(pghead);
+		}
 	}
 #ifdef MDB_VL32
 	if (!txn->mt_parent) {
@@ -3486,6 +3509,11 @@ _mdb_txn_abort(MDB_txn *txn)
 	if (txn == NULL)
 		return;
 
+	if (txn->mt_parent && txn->mt_flags & MDB_RDONLY) {
+		// You must first abort the child before the parent
+		mdb_tassert(txn, txn->mt_parent && atomic_load(&txn->mt_rdonly_child_count) == 0);
+	}
+
 	if (txn->mt_child)
 		_mdb_txn_abort(txn->mt_child);
 
@@ -6480,7 +6508,7 @@ mdb_page_get(MDB_cursor *mc, pgno_t pgno, MDB_page **ret, int *lvl)
 	MDB_page *p = NULL;
 	int level;
 
-	if (! (mc->mc_flags & (C_ORIG_RDONLY|C_WRITEMAP))) {
+	if (! (( mc->mc_flags & (C_ORIG_RDONLY|C_WRITEMAP) ) && mc->mc_txn->mt_parent == NULL)) {
 		MDB_txn *tx2 = txn;
 		level = 1;
 		do {
@@ -9628,7 +9656,7 @@ mdb_cursor_del0(MDB_cursor *mc)
 						goto fail;
 				}
 				if (m3->mc_xcursor && !(m3->mc_flags & C_EOF)) {
-					MDB_node *node = NODEPTR(m3->mc_pg[m3->mc_top], m3->mc_ki[m3->mc_top]);
+					MDB_node *node = NODEPTR(m3->mc_pg[mc->mc_top], m3->mc_ki[mc->mc_top]);
 					/* If this node has dupdata, it may need to be reinited
 					 * because its data has moved.
 					 * If the xcursor was not initd it must be reinited.