diff --git a/modules/openapi-generator/src/main/resources/csharp-netcore/modelGeneric.mustache b/modules/openapi-generator/src/main/resources/csharp-netcore/modelGeneric.mustache
index 3e554c1f980..cedfad4874b 100644
--- a/modules/openapi-generator/src/main/resources/csharp-netcore/modelGeneric.mustache
+++ b/modules/openapi-generator/src/main/resources/csharp-netcore/modelGeneric.mustache
@@ -178,6 +178,7 @@
             {{/conditionalSerialization}}
             {{#conditionalSerialization}}
             this._{{name}} = {{#lambda.camelcase_param}}{{name}}{{/lambda.camelcase_param}};
+            if (this.{{name}} != null) this._flag{{name}} = true;
             {{/conditionalSerialization}}
             {{/defaultValue}}
             {{/required}}