diff --git a/runners/google-cloud-dataflow-java/worker/src/main/java/org/apache/beam/runners/dataflow/worker/WindmillTimeUtils.java b/runners/google-cloud-dataflow-java/worker/src/main/java/org/apache/beam/runners/dataflow/worker/WindmillTimeUtils.java
index 8552c27d5967e..9c015cbf57621 100644
--- a/runners/google-cloud-dataflow-java/worker/src/main/java/org/apache/beam/runners/dataflow/worker/WindmillTimeUtils.java
+++ b/runners/google-cloud-dataflow-java/worker/src/main/java/org/apache/beam/runners/dataflow/worker/WindmillTimeUtils.java
@@ -44,6 +44,10 @@ public class WindmillTimeUtils {
   public static Instant windmillToHarnessTimestamp(long timestampUs) {
     // Windmill should never send us an unknown timestamp.
     Preconditions.checkArgument(timestampUs != Long.MIN_VALUE);
+    // Set windmill min timestamp to beam min timestamp
+    if(timestampUs == Long.MIN_VALUE +1){
+      return BoundedWindow.TIMESTAMP_MIN_VALUE;
+    }
     Instant result = new Instant(divideAndRoundDown(timestampUs, 1000));
     if (result.isAfter(BoundedWindow.TIMESTAMP_MAX_VALUE)) {
       // End of time.
diff --git a/runners/google-cloud-dataflow-java/worker/src/test/java/org/apache/beam/runners/dataflow/worker/WindmillTimeUtilsTest.java b/runners/google-cloud-dataflow-java/worker/src/test/java/org/apache/beam/runners/dataflow/worker/WindmillTimeUtilsTest.java
index 5f910c3acb5f5..940f2b8f6a895 100644
--- a/runners/google-cloud-dataflow-java/worker/src/test/java/org/apache/beam/runners/dataflow/worker/WindmillTimeUtilsTest.java
+++ b/runners/google-cloud-dataflow-java/worker/src/test/java/org/apache/beam/runners/dataflow/worker/WindmillTimeUtilsTest.java
@@ -56,6 +56,7 @@ public void testWindmillToHarnessTimestamp() {
     assertEquals(new Instant(-17), windmillToHarnessTimestamp(-16987));
     assertEquals(new Instant(-17), windmillToHarnessTimestamp(-17000));
     assertEquals(new Instant(-18), windmillToHarnessTimestamp(-17001));
+    assertEquals(BoundedWindow.TIMESTAMP_MIN_VALUE, windmillToHarnessTimestamp(Long.MIN_VALUE + 1));
   }
 
   @Test