diff --git a/generator/templates/webgpu_cpp.h b/generator/templates/webgpu_cpp.h
index f72e142..eb48a32 100644
--- a/generator/templates/webgpu_cpp.h
+++ b/generator/templates/webgpu_cpp.h
@@ -143,6 +143,8 @@
 {% macro render_cpp_default_value(member) -%}
     {%- if member.annotation in ["*", "const*", "const*const*"] and member.optional -%}
         {{" "}}= nullptr
+    {%- elif member.type.category == "object" and member.optional -%}
+        {{" "}}= nullptr
     {%- elif member.type.category in ["enum", "bitmask"] and member.default_value != None -%}
         {{" "}}= {{as_cppType(member.type.name)}}::{{as_cppEnum(Name(member.default_value))}}
     {%- elif member.type.category == "native" and member.default_value != None -%}