2 files changed, 7 insertions, 4 deletions
diff --git a/source/blender/render/intern/bake.c b/source/blender/render/intern/bake.c
index 74e9662d5db..d6e612ee061 100644
--- a/source/blender/render/intern/bake.c
+++ b/source/blender/render/intern/bake.c
@@ -740,14 +740,15 @@ void RE_bake_pixels_populate(Mesh *me,
 
   BKE_mesh_recalc_looptri(me->mloop, me->mpoly, me->mvert, me->totloop, me->totpoly, looptri);
 
+  const int *material_indices = BKE_mesh_material_indices(me);
+
   for (int i = 0; i < tottri; i++) {
     const MLoopTri *lt = &looptri[i];
-    const MPoly *mp = &me->mpoly[lt->poly];
 
     bd.primitive_id = i;
 
     /* Find images matching this material. */
-    Image *image = targets->material_to_image[mp->mat_nr];
+    Image *image = targets->material_to_image[material_indices ? material_indices[lt->poly] : 0];
     for (int image_id = 0; image_id < targets->images_num; image_id++) {
       BakeImage *bk_image = &targets->images[image_id];
       if (bk_image->image != image) {
diff --git a/source/blender/render/intern/multires_bake.c b/source/blender/render/intern/multires_bake.c
index e3229e20595..e116f41321f 100644
--- a/source/blender/render/intern/multires_bake.c
+++ b/source/blender/render/intern/multires_bake.c
@@ -63,6 +63,7 @@ typedef struct {
   MVert *mvert;
   const float (*vert_normals)[3];
   MPoly *mpoly;
+  const int *material_indices;
   MLoop *mloop;
   MLoopUV *mloopuv;
   float uv_offset[2];
@@ -382,8 +383,7 @@ static void *do_multires_bake_thread(void *data_v)
 
   while ((tri_index = multires_bake_queue_next_tri(handle->queue)) >= 0) {
     const MLoopTri *lt = &data->mlooptri[tri_index];
-    const MPoly *mp = &data->mpoly[lt->poly];
-    const short mat_nr = mp->mat_nr;
+    const short mat_nr = data->material_indices == NULL ? 0 : data->material_indices[lt->poly];
     const MLoopUV *mloopuv = data->mloopuv;
 
     if (multiresbake_test_break(bkr)) {
@@ -545,6 +545,8 @@ static void do_multires_bake(MultiresBakeRender *bkr,
     handle->queue = &queue;
 
     handle->data.mpoly = mpoly;
+    handle->data.material_indices = CustomData_get_layer_named(
+        &dm->polyData, CD_PROP_INT32, "material_index");
     handle->data.mvert = mvert;
     handle->data.vert_normals = vert_normals;
     handle->data.mloopuv = mloopuv;