diff --git a/libraries/liblmdb/mdb.c b/libraries/liblmdb/mdb.c
index ecf29bf..6e0fbf0 100644
--- a/libraries/liblmdb/mdb.c
+++ b/libraries/liblmdb/mdb.c
@@ -385,8 +385,7 @@ static txnid_t mdb_debug_start;
 	/**	@brief The maximum size of a key we can write to a database.
 	 *
 	 *	We require that keys all fit onto a regular page. This limit
-	 *	could be raised a bit further if needed; to something just
-	 *	under (page size / #MDB_MINKEYS / 3).
+	 *	can be raised to page size / #MDB_MINKEYS - (64-bit ? 66 : 44).
 	 *
 	 *	Note that data items in an #MDB_DUPSORT database are actually keys
 	 *	of a subDB, so they're also limited to this size.
@@ -5666,9 +5665,11 @@ mdb_cursor_put(MDB_cursor *mc, MDB_val *key, MDB_val *data,
 	enum { MDB_NO_ROOT = MDB_LAST_ERRCODE+10 }; /* internal code */
 	MDB_env		*env = mc->mc_txn->mt_env;
 	MDB_node	*leaf = NULL;
-	MDB_val	xdata, *rdata, dkey;
+	MDB_page	*fp, *mp;
+	uint16_t	fp_flags;
+	MDB_val		xdata, *rdata, dkey, olddata;
 	MDB_db dummy;
-	int do_sub = 0, insert = 0;
+	int do_sub = 0, insert;
 	unsigned int mcount = 0, dcount = 0, nospill;
 	size_t nsize;
 	int rc, rc2;
@@ -5782,11 +5783,21 @@ mdb_cursor_put(MDB_cursor *mc, MDB_val *key, MDB_val *data,
 			return rc2;
 	}
 
-	/* The key already exists */
-	if (rc == MDB_SUCCESS) {
-		MDB_page	*fp, *mp;
-		MDB_val		olddata;
-
+	insert = rc;
+	if (insert) {
+		/* The key does not exist */
+		DPRINTF(("inserting key at index %i", mc->mc_ki[mc->mc_top]));
+		if ((mc->mc_db->md_flags & MDB_DUPSORT) &&
+			LEAFSIZE(key, data) > env->me_nodemax)
+		{
+			/* Too big for a node, insert in sub-DB */
+			fp_flags = P_LEAF|P_DIRTY;
+			fp = env->me_pbuf;
+			fp->mp_pad = data->mv_size; /* used if MDB_DUPFIXED */
+			fp->mp_lower = fp->mp_upper = olddata.mv_size = PAGEHDRSZ;
+			goto prep_subDB;
+		}
+	} else {
 		/* there's only a key anyway, so this is a no-op */
 		if (IS_LEAF2(mc->mc_pg[mc->mc_top])) {
 			unsigned int ksize = mc->mc_db->md_pad;
@@ -5806,6 +5817,12 @@ more:
 
 		/* DB has dups? */
 		if (F_ISSET(mc->mc_db->md_flags, MDB_DUPSORT)) {
+			/* Prepare (sub-)page/sub-DB to accept the new item,
+			 * if needed.  fp: old sub-page or a header faking
+			 * it.  mp: new (sub-)page.  offset: growth in page
+			 * size.  xdata: node data with new page or DB.
+			 */
+			unsigned	i, offset = 0;
 			mp = fp = xdata.mv_data = env->me_pbuf;
 			mp->mp_pgno = mc->mc_pg[mc->mc_top]->mp_pgno;
 
@@ -5851,16 +5868,13 @@ more:
 						(dkey.mv_size & 1) + (data->mv_size & 1);
 				}
 				fp->mp_upper = xdata.mv_size;
+				olddata.mv_size = fp->mp_upper; /* pretend olddata is fp */
 			} else if (leaf->mn_flags & F_SUBDATA) {
 				/* Data is on sub-DB, just store it */
 				flags |= F_DUPDATA|F_SUBDATA;
 				goto put_sub;
 			} else {
-				/* See if we need to convert from fake page to subDB */
-				unsigned int offset;
-				unsigned int i;
-				uint16_t fp_flags;
-
+				/* Data is on sub-page */
 				fp = olddata.mv_data;
 				switch (flags) {
 				default:
@@ -5882,11 +5896,16 @@ more:
 					flags |= F_DUPDATA;
 					goto put_sub;
 				}
-				fp_flags = fp->mp_flags;
 				xdata.mv_size = olddata.mv_size + offset;
-				if (NODESIZE+NODEKSZ(leaf)+xdata.mv_size > env->me_nodemax) {
-					/* yes, convert it */
+			}
+
+			fp_flags = fp->mp_flags;
+			if (NODESIZE + NODEKSZ(leaf) + xdata.mv_size > env->me_nodemax) {
+					/* Too big for a sub-page, convert to sub-DB */
+					fp_flags &= ~P_SUBP;
+prep_subDB:
 					if (mc->mc_db->md_flags & MDB_DUPFIXED) {
+						fp_flags |= P_LEAF2;
 						dummy.md_pad = fp->mp_pad;
 						dummy.md_flags = MDB_DUPFIXED;
 						if (mc->mc_db->md_flags & MDB_INTEGERDUP)
@@ -5907,13 +5926,13 @@ more:
 					offset = env->me_psize - olddata.mv_size;
 					flags |= F_DUPDATA|F_SUBDATA;
 					dummy.md_root = mp->mp_pgno;
-					fp_flags &= ~P_SUBP;
-				}
+			}
+			if (mp != fp) {
 				mp->mp_flags = fp_flags | P_DIRTY;
 				mp->mp_pad   = fp->mp_pad;
 				mp->mp_lower = fp->mp_lower;
 				mp->mp_upper = fp->mp_upper + offset;
-				if (IS_LEAF2(fp)) {
+				if (fp_flags & P_LEAF2) {
 					memcpy(METADATA(mp), METADATA(fp), NUMKEYS(fp) * fp->mp_pad);
 				} else {
 					memcpy((char *)mp + mp->mp_upper, (char *)fp + fp->mp_upper,
@@ -6004,9 +6023,6 @@ current:
 		}
 		mdb_node_del(mc->mc_pg[mc->mc_top], mc->mc_ki[mc->mc_top], 0);
 		mc->mc_db->md_entries--;
-	} else {
-		DPRINTF(("inserting key at index %i", mc->mc_ki[mc->mc_top]));
-		insert = 1;
 	}
 
 	rdata = data;