diff --git a/modules/openapi-generator/src/main/resources/typescript-fetch/modelGeneric.mustache b/modules/openapi-generator/src/main/resources/typescript-fetch/modelGeneric.mustache
index 0d36547cfc2..1524de8b94c 100644
--- a/modules/openapi-generator/src/main/resources/typescript-fetch/modelGeneric.mustache
+++ b/modules/openapi-generator/src/main/resources/typescript-fetch/modelGeneric.mustache
@@ -118,7 +118,22 @@ export function {{classname}}ToJSON(value?: {{classname}} | null): any {
         {{#vars}}
         {{^isReadOnly}}
         {{#isPrimitiveType}}
-        '{{baseName}}': {{#isDateType}}{{^required}}value.{{name}} === undefined ? undefined : {{/required}}({{#isNullable}}value.{{name}} === null ? null : {{/isNullable}}value.{{name}}.toISOString().substr(0,10)){{/isDateType}}{{#isDateTimeType}}{{^required}}value.{{name}} === undefined ? undefined : {{/required}}({{#isNullable}}value.{{name}} === null ? null : {{/isNullable}}value.{{name}}.toISOString()){{/isDateTimeType}}{{^isDateType}}{{^isDateTimeType}}value.{{name}}{{/isDateTimeType}}{{/isDateType}},
+        {{#isDateType}}
+        '{{baseName}}': {{^required}}value.{{name}} === undefined ? undefined : {{/required}}({{#isNullable}}value.{{name}} === null ? null : {{/isNullable}}value.{{name}}.toISOString().substr(0,10)),
+        {{/isDateType}}
+        {{#isDateTimeType}}
+        '{{baseName}}': {{^required}}value.{{name}} === undefined ? undefined : {{/required}}({{#isNullable}}value.{{name}} === null ? null : {{/isNullable}}value.{{name}}.toISOString()),
+        {{/isDateTimeType}}
+        {{#isArray}}
+        '{{baseName}}': {{#uniqueItems}}{{^required}}value.{{name}} === undefined ? undefined : {{/required}}{{#isNullable}}value.{{name}} === null ? null : {{/isNullable}}Array.from(value.{{name}} as Set<any>){{/uniqueItems}}{{^uniqueItems}}value.{{name}}{{/uniqueItems}},
+        {{/isArray}}
+        {{^isDateType}}
+        {{^isDateTimeType}}
+        {{^isArray}}
+        '{{baseName}}': value.{{name}},
+        {{/isArray}}
+        {{/isDateTimeType}}
+        {{/isDateType}}
         {{/isPrimitiveType}}
         {{^isPrimitiveType}}
         {{#isArray}}
diff --git a/samples/client/petstore/typescript-fetch/builds/default-v3.0/models/Pet.ts b/samples/client/petstore/typescript-fetch/builds/default-v3.0/models/Pet.ts
index f7dc9744111..33e2b6db797 100644
--- a/samples/client/petstore/typescript-fetch/builds/default-v3.0/models/Pet.ts
+++ b/samples/client/petstore/typescript-fetch/builds/default-v3.0/models/Pet.ts
@@ -124,7 +124,7 @@ export function PetToJSON(value?: Pet | null): any {
         'id': value.id,
         'category': CategoryToJSON(value.category),
         'name': value.name,
-        'photoUrls': value.photoUrls,
+        'photoUrls': Array.from(value.photoUrls as Set<any>),
         'tags': value.tags === undefined ? undefined : ((value.tags as Array<any>).map(TagToJSON)),
         'status': value.status,
     };