diff --git a/src/api/signature/payload.rs b/src/api/signature/payload.rs
index 1e3fa207..b50fb3bb 100644
--- a/src/api/signature/payload.rs
+++ b/src/api/signature/payload.rs
@@ -211,7 +211,7 @@ fn parse_query_authorization(
 fn parse_credential(cred: &str) -> Result<(String, String), Error> {
 	let first_slash = cred
 		.find('/')
-		.ok_or_bad_request("Credentials does not contain / in authorization field")?;
+		.ok_or_bad_request("Credentials does not contain '/' in authorization field")?;
 	let (key_id, scope) = cred.split_at(first_slash);
 	Ok((
 		key_id.to_string(),