diff --git a/tor-llcrypto/src/pk/rsa.rs b/tor-llcrypto/src/pk/rsa.rs
index 72e35af3d..26d78e556 100644
--- a/tor-llcrypto/src/pk/rsa.rs
+++ b/tor-llcrypto/src/pk/rsa.rs
@@ -223,7 +223,7 @@ impl PublicKey {
         }
 
         let asn1 = ASN1Block::Sequence(0, vec![to_asn1_int(self.0.n()), to_asn1_int(self.0.e())]);
-        simple_asn1::to_der(&asn1).unwrap()
+        simple_asn1::to_der(&asn1).expect("RSA key not encodeable as DER")
     }
 
     /// Compute the RSAIdentity for this public key.