diff --git a/sdks/java/core/src/main/java/org/apache/beam/sdk/testing/TestStream.java b/sdks/java/core/src/main/java/org/apache/beam/sdk/testing/TestStream.java
index e10f0a558399..f7b08f0b135a 100644
--- a/sdks/java/core/src/main/java/org/apache/beam/sdk/testing/TestStream.java
+++ b/sdks/java/core/src/main/java/org/apache/beam/sdk/testing/TestStream.java
@@ -199,7 +199,7 @@ public Builder<T> advanceWatermarkTo(Instant newWatermark) {
     public Builder<T> advanceProcessingTime(Duration amount) {
       checkArgument(
           amount.getMillis() > 0,
-          "Must advance the processing time by a positive amount. Got: ",
+          "Must advance the processing time by a positive amount. Got: %s",
           amount);
       ImmutableList<Event<T>> newEvents =
           ImmutableList.<Event<T>>builder()