diff --git a/plugin/src/main/java/org/elasticsearch/xpack/ml/job/process/DataStreamDiagnostics.java b/plugin/src/main/java/org/elasticsearch/xpack/ml/job/process/DataStreamDiagnostics.java
index 2ff9be9af77..524b111ef23 100644
--- a/plugin/src/main/java/org/elasticsearch/xpack/ml/job/process/DataStreamDiagnostics.java
+++ b/plugin/src/main/java/org/elasticsearch/xpack/ml/job/process/DataStreamDiagnostics.java
@@ -81,7 +81,9 @@ public class DataStreamDiagnostics {
      */
     public void flush() {
         // flush all we know
-        flush(movingBucketHistogram.lastKey() + 1);
+        if (movingBucketHistogram.isEmpty() == false) {
+            flush(movingBucketHistogram.lastKey() + 1);
+        }
     }
 
     /**
diff --git a/plugin/src/test/java/org/elasticsearch/xpack/ml/job/process/DataStreamDiagnosticsTests.java b/plugin/src/test/java/org/elasticsearch/xpack/ml/job/process/DataStreamDiagnosticsTests.java
index eccd712c1c0..7b80febdf20 100644
--- a/plugin/src/test/java/org/elasticsearch/xpack/ml/job/process/DataStreamDiagnosticsTests.java
+++ b/plugin/src/test/java/org/elasticsearch/xpack/ml/job/process/DataStreamDiagnosticsTests.java
@@ -259,6 +259,12 @@ public class DataStreamDiagnosticsTests extends ESTestCase {
         assertEquals(null, d.getLatestEmptyBucketTime());
     }
 
+    public void testFlushAfterZeroRecords() {
+        DataStreamDiagnostics d = new DataStreamDiagnostics(job);
+        d.flush();
+        assertEquals(0, d.getBucketCount());
+    }
+
     private void sendManyDataPoints(DataStreamDiagnostics d, long recordTimestampInMsMin, long recordTimestampInMsMax, long howMuch) {
 
         long range = recordTimestampInMsMax - recordTimestampInMsMin;