diff --git a/flink-runtime/src/test/java/org/apache/flink/runtime/rest/RestClientTest.java b/flink-runtime/src/test/java/org/apache/flink/runtime/rest/RestClientTest.java
index 040a10b543114..25d685e3189b6 100644
--- a/flink-runtime/src/test/java/org/apache/flink/runtime/rest/RestClientTest.java
+++ b/flink-runtime/src/test/java/org/apache/flink/runtime/rest/RestClientTest.java
@@ -77,7 +77,8 @@ class RestClientTest {
     private static final TestExecutorExtension<ScheduledExecutorService> EXECUTOR_EXTENSION =
             TestingUtils.defaultExecutorExtension();
 
-    private static final String unroutableIp = "240.0.0.0";
+    // Part of TEST-NET-1 block described in RFC 5737 that should never be routed.
+    private static final String unroutableIp = "192.0.2.1";
 
     private static final long TIMEOUT = 10L;