diff --git a/__crypto/jose-test/src/jose.rs b/__crypto/jose-test/src/jose.rs
index 7ca3376..ac81d92 100644
--- a/__crypto/jose-test/src/jose.rs
+++ b/__crypto/jose-test/src/jose.rs
@@ -159,7 +159,7 @@ fn serialize_jwe_fn<F>(header: &JweHeader2, payload: &[u8], key_wrap_fn: F) -> X
 where
     F: Fn(&[u8]) -> XResult<Vec<u8>>,
 {
-    let header_str = serde_json::to_string(&header).unwrap();
+    let header_str = opt_result!(serde_json::to_string(&header), "Invalid JWE header: {}");
     let header_b64 = URL_SAFE_NO_PAD.encode(header_str.as_bytes());
 
     let data_key: [u8; 32] = random();