diff --git a/flink-runtime/src/main/java/org/apache/flink/runtime/checkpoint/savepoint/SavepointV2Serializer.java b/flink-runtime/src/main/java/org/apache/flink/runtime/checkpoint/savepoint/SavepointV2Serializer.java
index c8d695f380d1198f0b8cf8d33d2f844ff4337fb8..4cbbfcfba8b5b17490cfa9560172fe4ebd0f1d77 100644
--- a/flink-runtime/src/main/java/org/apache/flink/runtime/checkpoint/savepoint/SavepointV2Serializer.java
+++ b/flink-runtime/src/main/java/org/apache/flink/runtime/checkpoint/savepoint/SavepointV2Serializer.java
@@ -39,6 +39,7 @@ import java.io.ByteArrayOutputStream;
 import java.io.DataInputStream;
 import java.io.DataOutputStream;
 import java.io.IOException;
+import java.nio.charset.StandardCharsets;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Collections;
@@ -391,8 +392,17 @@ class SavepointV2Serializer implements SavepointSerializer<SavepointV2> {
 			Map<StateHandleID, StreamStateHandle> sharedStates = deserializeStreamStateHandleMap(dis);
 			Map<StateHandleID, StreamStateHandle> privateStates = deserializeStreamStateHandleMap(dis);
 
+			UUID uuid;
+
+			try {
+				uuid = UUID.fromString(backendId);
+			} catch (Exception ex) {
+				// compatibility with old format pre FLINK-6964:
+				uuid = UUID.nameUUIDFromBytes(backendId.getBytes(StandardCharsets.UTF_8));
+			}
+
 			return new IncrementalKeyedStateHandle(
-				UUID.fromString(backendId),
+				uuid,
 				keyGroupRange,
 				checkpointId,
 				sharedStates,
diff --git a/flink-runtime/src/test/scala/org/apache/flink/runtime/testingUtils/TestingCluster.scala b/flink-runtime/src/test/scala/org/apache/flink/runtime/testingUtils/TestingCluster.scala
index 48c4d858c73a1d00d0ce51238a32bd398938590a..833cb61d6fe8e2ebedf8dd393d78b2f7bb5d4791 100644
--- a/flink-runtime/src/test/scala/org/apache/flink/runtime/testingUtils/TestingCluster.scala
+++ b/flink-runtime/src/test/scala/org/apache/flink/runtime/testingUtils/TestingCluster.scala
@@ -378,12 +378,6 @@ class TestingCluster(
   def requestCheckpoint(jobId: JobID, options : CheckpointOptions): String = {
     val jobManagerGateway = getLeaderGateway(timeout)
 
-    // wait until the cluster is ready to take a checkpoint.
-    val allRunning = jobManagerGateway.ask(
-      TestingJobManagerMessages.WaitForAllVerticesToBeRunning(jobId), timeout)
-
-    Await.ready(allRunning, timeout)
-
     // trigger checkpoint
     val result = Await.result(
       jobManagerGateway.ask(CheckpointRequest(jobId, options), timeout), timeout)
@@ -395,16 +389,9 @@ class TestingCluster(
         // failed because tasks were not ready.This would not be required if
         // TestingJobManagerMessages.WaitForAllVerticesToBeRunning(...) works
         // properly.
-        if (fail.cause != null) {
-          val innerCause = fail.cause.getCause
-          if (innerCause != null
-            && innerCause.getMessage.contains("tasks not ready")) {
-            // retry if the tasks are not ready yet.
-            Thread.sleep(50)
-            return requestCheckpoint(jobId, options)
-          }
-        }
-        throw new IOException(fail.cause)
+        LOG.info("Test checkpoint attempt failed. Retry ...", fail.cause)
+        Thread.sleep(50)
+        requestCheckpoint(jobId, options)
       }
       case _ => throw new IllegalStateException("Trigger checkpoint failed")
     }