diff --git a/x-pack/plugin/security/src/main/java/org/elasticsearch/xpack/security/authc/RealmsAuthenticator.java b/x-pack/plugin/security/src/main/java/org/elasticsearch/xpack/security/authc/RealmsAuthenticator.java
index 2968588b75d17..80931e5aebc9a 100644
--- a/x-pack/plugin/security/src/main/java/org/elasticsearch/xpack/security/authc/RealmsAuthenticator.java
+++ b/x-pack/plugin/security/src/main/java/org/elasticsearch/xpack/security/authc/RealmsAuthenticator.java
@@ -259,7 +259,7 @@ private static void consumeNullUser(
         messages.forEach((realm, tuple) -> {
             final String message = tuple.v1();
             final String cause = tuple.v2() == null ? "" : " (Caused by " + tuple.v2() + ")";
-            logger.debug("Authentication to realm {} failed - {}{}", realm.name(), message, cause);
+            logger.warn("Authentication to realm {} failed - {}{}", realm.name(), message, cause);
         });
         if (context.getUnlicensedRealms().isEmpty() == false) {
             logger.warn(