diff --git a/java/com/google/gerrit/server/schema/Schema_146.java b/java/com/google/gerrit/server/schema/Schema_146.java
index d05c5f560a..e0127c047f 100644
--- a/java/com/google/gerrit/server/schema/Schema_146.java
+++ b/java/com/google/gerrit/server/schema/Schema_146.java
@@ -42,6 +42,7 @@ import java.util.Map.Entry;
 import java.util.Set;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicInteger;
 import java.util.concurrent.locks.ReentrantLock;
@@ -105,7 +106,12 @@ public class Schema_146 extends SchemaVersion {
         Sets.newHashSet(Iterables.partition(accounts, 500));
     ExecutorService pool = createExecutor(ui);
     try {
-      batches.stream().forEach(batch -> pool.submit(() -> processBatch(db, batch, ui)));
+      batches.stream()
+          .forEach(
+              batch -> {
+                @SuppressWarnings("unused")
+                Future<?> unused = pool.submit(() -> processBatch(db, batch, ui));
+              });
       pool.shutdown();
       pool.awaitTermination(Long.MAX_VALUE, TimeUnit.DAYS);
     } catch (InterruptedException e) {