diff --git a/generate/aff.mjs b/generate/aff.mjs
index a5dec2ef3..09f107a0e 100644
--- a/generate/aff.mjs
+++ b/generate/aff.mjs
@@ -32,10 +32,10 @@ async function run() {
     fs.writeFileSync(filename, result.get());
 
 
-    const command = `diff --strip-trailing-cr generated/${type.toLowerCase()}-v1.json ../file-formats/${type.toLowerCase()}/${type.toLowerCase()}-v1.json`;
+    const command = `diff --strip-trailing-cr -u generated/${type.toLowerCase()}-v1.json ../file-formats/${type.toLowerCase()}/${type.toLowerCase()}-v1.json`;
     const output = child_process.execSync(`${command} || true`);
     if (output.toString().length > 0) {
-      core.error("Provided and generated JSON Schema differ "+type)
+      core.setFailed("Provided and generated JSON Schema differ "+type)
       core.info(command);
       core.info(output.toString());
     } else {