diff --git a/source/blender/gpu/metal/mtl_shader_generator.mm b/source/blender/gpu/metal/mtl_shader_generator.mm
index d0077cb5a9b..d9b17597364 100644
--- a/source/blender/gpu/metal/mtl_shader_generator.mm
+++ b/source/blender/gpu/metal/mtl_shader_generator.mm
@@ -3166,10 +3166,11 @@ std::string MSLGeneratorInterface::generate_msl_vertex_attribute_input_populatio
           &do_attribute_conversion_on_read, this->vertex_input_attributes[attribute].type);
 
       if (do_attribute_conversion_on_read) {
-        out << "\t" << attribute_conversion_func_name << "(MTL_AttributeConvert" << attribute
-            << ", v_in." << this->vertex_input_attributes[attribute].name << ", "
-            << shader_stage_inst_name << "." << this->vertex_input_attributes[attribute].name
-            << ");" << std::endl;
+        BLI_assert(this->vertex_input_attributes[attribute].layout_location >= 0);
+        out << "\t" << attribute_conversion_func_name << "(MTL_AttributeConvert"
+            << this->vertex_input_attributes[attribute].layout_location << ", v_in."
+            << this->vertex_input_attributes[attribute].name << ", " << shader_stage_inst_name
+            << "." << this->vertex_input_attributes[attribute].name << ");" << std::endl;
       }
       else {
         out << "\t" << shader_stage_inst_name << "."