2 files changed, 20 insertions, 0 deletions
diff --git a/source/blender/bmesh/intern/bmesh_mesh_conv.c b/source/blender/bmesh/intern/bmesh_mesh_conv.c
index 9bcc9b9e84b..4e65ac40dd4 100644
--- a/source/blender/bmesh/intern/bmesh_mesh_conv.c
+++ b/source/blender/bmesh/intern/bmesh_mesh_conv.c
@@ -972,6 +972,16 @@ void BM_mesh_bm_to_me(Main *bmain, BMesh *bm, Mesh *me, const struct BMeshToMesh
     if (ofs) {
       MEM_freeN(ofs);
     }
+
+    if (params->update_shapekey_indices) {
+      /* We have written a new shape key, if this mesh is _not_ going to be freed,
+       * update the shape key indices to match the newly updated. */
+      if (cd_shape_keyindex_offset != -1) {
+        BM_ITER_MESH_INDEX (eve, &iter, bm, BM_VERTS_OF_MESH, i) {
+          BM_ELEM_CD_SET_INT(eve, cd_shape_keyindex_offset, i);
+        }
+      }
+    }
   }
 
   if (oldverts != NULL) {
diff --git a/source/blender/bmesh/intern/bmesh_mesh_conv.h b/source/blender/bmesh/intern/bmesh_mesh_conv.h
index f0302764a5f..65d5c6d5494 100644
--- a/source/blender/bmesh/intern/bmesh_mesh_conv.h
+++ b/source/blender/bmesh/intern/bmesh_mesh_conv.h
@@ -48,6 +48,16 @@ void BM_mesh_bm_from_me(BMesh *bm, const struct Mesh *me, const struct BMeshFrom
 struct BMeshToMeshParams {
   /** Update object hook indices & vertex parents. */
   uint calc_object_remap : 1;
+  /**
+   * This re-assigns shape-key indices. Only do if the BMesh will have continued use
+   * to update the mesh & shape key in the future.
+   * In the case the BMesh is freed immediately, this can be left false.
+   *
+   * This is needed when flushing changes from edit-mode into object mode,
+   * so a second flush or edit-mode exit doesn't run with indices
+   * that have become invalid from updating the shape-key, see T71865.
+   */
+  uint update_shapekey_indices : 1;
   struct CustomData_MeshMasks cd_mask_extra;
 };
 void BM_mesh_bm_to_me(struct Main *bmain,