diff --git a/source/blender/editors/mesh/meshtools.c b/source/blender/editors/mesh/meshtools.c
index 7faa1dd99e1..3f06ba2ced4 100644
--- a/source/blender/editors/mesh/meshtools.c
+++ b/source/blender/editors/mesh/meshtools.c
@@ -104,22 +104,26 @@ static void join_mesh_single(
 
 		/* vertex groups */
 		MDeformVert *dvert = CustomData_get(vdata, *vertofs, CD_MDEFORMVERT);
+		MDeformVert *dvert_src = CustomData_get(&me->vdata, 0, CD_MDEFORMVERT);
 
-		/* NB: vertex groups here are new version */
-		if (dvert) {
-			for (a = 0; a < me->totvert; a++) {
-				for (b = 0; b < dvert[a].totweight; b++) {
-					/*	Find the old vertex group */
-					bDeformGroup *dg, *odg = BLI_findlink(&base_src->object->defbase, dvert[a].dw[b].def_nr);
-					int index;
-					if (odg) {
-						/*	Search for a match in the new object, and set new index */
-						for (dg = ob_dst->defbase.first, index = 0; dg; dg = dg->next, index++) {
-							if (STREQ(dg->name, odg->name)) {
-								dvert[a].dw[b].def_nr = index;
-								break;
-							}
-						}
+		/* Remap to correct new vgroup indices, if needed. */
+		if (dvert_src) {
+			BLI_assert(dvert != NULL);
+
+			/* Build src to merged mapping of vgroup indices. */
+			bDeformGroup *dg_src;
+			int *vgroup_index_map = alloca(sizeof(*vgroup_index_map) * BLI_listbase_count(&base_src->object->defbase));
+			bool is_vgroup_remap_needed = false;
+
+			for (dg_src = base_src->object->defbase.first, b = 0; dg_src; dg_src = dg_src->next, b++) {
+				vgroup_index_map[b] = defgroup_name_index(ob_dst, dg_src->name);
+				is_vgroup_remap_needed = is_vgroup_remap_needed || (vgroup_index_map[b] != b);
+			}
+
+			if (is_vgroup_remap_needed) {
+				for (a = 0; a < me->totvert; a++) {
+					for (b = 0; b < dvert[a].totweight; b++) {
+						dvert[a].dw[b].def_nr = vgroup_index_map[dvert_src[a].dw[b].def_nr];
 					}
 				}
 			}