diff --git a/source/blender/editors/grease_pencil/intern/grease_pencil_pen.cc b/source/blender/editors/grease_pencil/intern/grease_pencil_pen.cc
index 16efcc2f53d..41f4ab723e9 100644
--- a/source/blender/editors/grease_pencil/intern/grease_pencil_pen.cc
+++ b/source/blender/editors/grease_pencil/intern/grease_pencil_pen.cc
@@ -665,7 +665,7 @@ struct PenToolOperation {
     curves.update_curve_types();
 
     const int material_index = this->vc.obact->actcol - 1;
-    if (material_index != 0) {
+    if (material_index != -1) {
       bke::SpanAttributeWriter<int> material_indexes =
           attributes.lookup_or_add_for_write_span<int>(
               "material_index",