diff --git a/source/blender/modifiers/intern/MOD_grease_pencil_util.cc b/source/blender/modifiers/intern/MOD_grease_pencil_util.cc
index 651f0c399ad..c18eb6cfc25 100644
--- a/source/blender/modifiers/intern/MOD_grease_pencil_util.cc
+++ b/source/blender/modifiers/intern/MOD_grease_pencil_util.cc
@@ -190,12 +190,13 @@ void draw_custom_curve_settings(const bContext * /*C*/, uiLayout *layout, Pointe
 static Vector<int> get_grease_pencil_material_passes(const Object *ob)
 {
   short *totcol = BKE_object_material_len_p(const_cast<Object *>(ob));
-  Vector<int> result(*totcol);
+  Vector<int> result(*totcol, 0);
   Material *ma = nullptr;
   for (short i = 0; i < *totcol; i++) {
-    ma = BKE_object_material_get(const_cast<Object *>(ob), i + 1);
-    /* Pass index of the grease pencil material. */
-    result[i] = ma->gp_style->index;
+    if (ma = BKE_object_material_get(const_cast<Object *>(ob), i + 1)) {
+      /* Pass index of the grease pencil material. */
+      result[i] = ma->gp_style->index;
+    }
   }
   return result;
 }