diff --git a/crates/ptth_relay/src/key_validity.rs b/crates/ptth_relay/src/key_validity.rs
index bc19223..dbe1c23 100644
--- a/crates/ptth_relay/src/key_validity.rs
+++ b/crates/ptth_relay/src/key_validity.rs
@@ -185,6 +185,11 @@ mod tests {
 		let j = json! ({
 			"tripcode": tripcode,
 		});
+		
+		let s = serde_json::to_string (&j).unwrap ();
+		
+		let j = serde_json::from_str::<serde_json::Value> (&s).unwrap ();
+		assert_eq! (j, json! ({"tripcode": tripcode}));
 	}
 	
 	#[test]