diff --git a/source/blender/makesrna/intern/rna_mesh.cc b/source/blender/makesrna/intern/rna_mesh.cc
index 5767c9c2702..6c2fc667139 100644
--- a/source/blender/makesrna/intern/rna_mesh.cc
+++ b/source/blender/makesrna/intern/rna_mesh.cc
@@ -941,10 +941,12 @@ static void rna_MeshUVLoopLayer_data_begin(CollectionPropertyIterator *iter, Poi
 {
   Mesh *mesh = rna_mesh(ptr);
   CustomDataLayer *layer = (CustomDataLayer *)ptr->data;
+  const int length = (mesh->runtime->edit_mesh) ? 0 : mesh->corners_num;
+  CustomData_ensure_data_is_mutable(layer, length);
   rna_iterator_array_begin(iter,
                            layer->data,
                            sizeof(float[2]),
-                           (mesh->runtime->edit_mesh) ? 0 : mesh->corners_num,
+                           length,
                            0,
                            nullptr);
 }