diff --git a/source/blender/modifiers/intern/MOD_screw.cc b/source/blender/modifiers/intern/MOD_screw.cc
index cf6f0c02955..45fe556e51f 100644
--- a/source/blender/modifiers/intern/MOD_screw.cc
+++ b/source/blender/modifiers/intern/MOD_screw.cc
@@ -878,7 +878,7 @@ static Mesh *modifyMesh(ModifierData *md, const ModifierEvalContext *ctx, Mesh *
       else {
         origindex[mpoly_index] = ORIGINDEX_NONE;
         dst_material_index[mpoly_index] = mat_nr;
-        sharp_faces.span[i] = use_flat_shading;
+        sharp_faces.span[mpoly_index] = use_flat_shading;
       }
       poly_offests_new[mpoly_index] = mpoly_index * 4;