diff --git a/test/Models/ThemeConfig/Conversion/PrepareTheme.spec.ts b/test/Models/ThemeConfig/Conversion/PrepareTheme.spec.ts
index ec4118934..ff22850be 100644
--- a/test/Models/ThemeConfig/Conversion/PrepareTheme.spec.ts
+++ b/test/Models/ThemeConfig/Conversion/PrepareTheme.spec.ts
@@ -173,6 +173,7 @@ describe("PrepareTheme", () => {
         }).convertStrict(layout, ConversionContext.test())
         expect(rewritten.layers[0]).toEqual(testLayer)
         expect(rewritten.layers[1]).toEqual({
+            "_basedOn": "layer-example",
             source: {
                 osmTags: "x=y",
             },