diff --git a/.changeset/old-news-raise.md b/.changeset/old-news-raise.md
new file mode 100644
index 0000000..7011e90
--- /dev/null
+++ b/.changeset/old-news-raise.md
@@ -0,0 +1,5 @@
+---
+"@tim-smart/openapi-gen": patch
+---
+
+Ensure 4xx Schema.Class generated even when schema empty.
diff --git a/src/JsonSchemaGen.ts b/src/JsonSchemaGen.ts
index c4988b0..deb197e 100644
--- a/src/JsonSchemaGen.ts
+++ b/src/JsonSchemaGen.ts
@@ -160,7 +160,9 @@ const make = Effect.gen(function* () {
       isClass,
       isEnum,
     })
-    return toSource(importName, schema, name, topLevel).pipe(
+    return toSource(importName, Object.keys(schema).length ? schema : {
+      properties: {},
+    } as JsonSchema.JsonSchema, name, topLevel).pipe(
       Option.map((source) =>
         transformer.onTopLevel({
           importName,