diff --git a/validator/src/main.rs b/validator/src/main.rs
index 5a969c4e43..3277ba4a43 100644
--- a/validator/src/main.rs
+++ b/validator/src/main.rs
@@ -1127,6 +1127,7 @@ pub fn main() {
                 .alias("no-untrusted-rpc")
                 .long("only-known-rpc")
                 .takes_value(false)
+                .requires("known_validators")
                 .help("Use the RPC service of known validators only")
         )
         .arg(