diff --git a/src/generators/plain.ts b/src/generators/plain.ts
index 1a313ba..9f1990d 100644
--- a/src/generators/plain.ts
+++ b/src/generators/plain.ts
@@ -112,11 +112,15 @@ export function stringifyPlain(
 
       if (!field.isRequired) {
         stringifiedType = wrapWithNullable(stringifiedType);
-        if (isInputModelCreate || isInputModelUpdate) {
+        if (isInputModelCreate) {
           stringifiedType = wrapWithOptional(stringifiedType);
         }
       }
 
+      if (isInputModelUpdate) {
+        stringifiedType = wrapWithOptional(stringifiedType);
+      }
+
       return `${field.name}: ${stringifiedType}`;
     })
     .filter((x) => x) as string[];