diff --git a/lcli/src/main.rs b/lcli/src/main.rs
index 00d0ab48e28..72d5cfd0a43 100644
--- a/lcli/src/main.rs
+++ b/lcli/src/main.rs
@@ -916,9 +916,9 @@ fn main() {
                     Arg::with_name("all-payloads-valid")
                         .long("all-payloads-valid")
                         .takes_value(true)
-                        .help("When set to true, the server will indicate that all payloads are \
-                            valid.")
-                        .default_value("true")
+                        .help("Controls the response to newPayload and forkchoiceUpdated. \
+                            Set to 'true' to return VALID. Set to 'false' to return SYNCING.")
+                        .default_value("false")
                 )
                 .arg(
                     Arg::with_name("shanghai-time")
diff --git a/lcli/src/mock_el.rs b/lcli/src/mock_el.rs
index 6b3b4baeca4..934b2db32c9 100644
--- a/lcli/src/mock_el.rs
+++ b/lcli/src/mock_el.rs
@@ -37,6 +37,10 @@ pub fn run<T: EthSpec>(mut env: Environment<T>, matches: &ArgMatches) -> Result<
     let server: MockServer<T> = MockServer::new_with_config(&handle, config);
 
     if all_payloads_valid {
+        eprintln!(
+            "Using --all-payloads-valid=true can be dangerous. \
+            Never use this flag when operating validators."
+        );
         // Indicate that all payloads are valid.
         server.all_payloads_valid();
     }