diff --git a/atlasdb-tests-shared/src/test/java/com/palantir/atlasdb/sweep/queue/TargetedSweepTest.java b/atlasdb-tests-shared/src/test/java/com/palantir/atlasdb/sweep/queue/TargetedSweepTest.java
index 42bdfa5c1fd..4fddf2cbd31 100644
--- a/atlasdb-tests-shared/src/test/java/com/palantir/atlasdb/sweep/queue/TargetedSweepTest.java
+++ b/atlasdb-tests-shared/src/test/java/com/palantir/atlasdb/sweep/queue/TargetedSweepTest.java
@@ -39,9 +39,11 @@
 import com.palantir.atlasdb.transaction.api.TransactionConflictException;
 import java.nio.charset.StandardCharsets;
 import java.util.List;
+import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicLong;
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
+import org.awaitility.Awaitility;
 import org.junit.Before;
 import org.junit.Test;
 import org.mockito.ArgumentCaptor;
@@ -174,6 +176,7 @@ public void sweepDeletesValuesWrittenOnPreCommitConditionFailure() {
         long startTs = putWriteAndFailOnPreCommitConditionReturningStartTimestamp(SINGLE_WRITE);
 
         serializableTxManager.setUnreadableTimestamp(startTs + 1);
+        waitForImmutableTimestampToBeStrictlyGreaterThan(startTs);
         sweepNextBatch(ShardAndStrategy.conservative(0));
         assertNoEntryForCellInKvs(TABLE_CONS, TEST_CELL);
     }
@@ -313,4 +316,30 @@ public void cleanup() {}
     private void sweepNextBatch(ShardAndStrategy shardStrategy) {
         sweepQueue.sweepNextBatch(shardStrategy, Sweeper.of(shardStrategy).getSweepTimestamp(sweepTimestampSupplier));
     }
+
+    /**
+     * After this method returns successfully, we know that there has existed some point in time when the immutable
+     * timestamp from the {@link #serializableTxManager} was strictly greater than the timestamp parameter that was
+     * passed. Note that in the general case, this does not guarantee that the immutable timestamp is currently
+     * greater than the timestamp parameter in the presence of concurrent transaction starts. This is because it may
+     * go backwards under certain (non-deterministic) scheduling conditions. Writers of sweep tests must ensure that
+     * this is the case when writing their tests.
+     *
+     * In the absence of concurrent transaction starts, however, this does guarantee that the immutable timestamp
+     * will be strictly greater than the timestamp parameter going forward. Test writers must ensure this is the case
+     * if they wish to meaningfully use this method.
+     *
+     * Some tests assert that Sweep has deleted values written by a given transaction. This requires the immutable
+     * timestamp to have progressed past the start timestamp of said transaction, which in turn requires that that
+     * transaction has released its immutable timestamp lock. Releasing this lock happens asynchronously.
+     *
+     * We thus perform an explicit wait before any iterations of Sweep which change state in a way that assertions
+     * depend on.
+     */
+    private void waitForImmutableTimestampToBeStrictlyGreaterThan(long timestampToBePassed) {
+        Awaitility.await()
+                .atMost(5, TimeUnit.SECONDS)
+                .pollInterval(10, TimeUnit.MILLISECONDS)
+                .until(() -> timestampToBePassed < serializableTxManager.getImmutableTimestamp());
+    }
 }
diff --git a/atlasdb-tests-shared/src/test/java/com/palantir/atlasdb/transaction/impl/SnapshotTransactionTest.java b/atlasdb-tests-shared/src/test/java/com/palantir/atlasdb/transaction/impl/SnapshotTransactionTest.java
index 2849190ebb4..69edf57bcee 100644
--- a/atlasdb-tests-shared/src/test/java/com/palantir/atlasdb/transaction/impl/SnapshotTransactionTest.java
+++ b/atlasdb-tests-shared/src/test/java/com/palantir/atlasdb/transaction/impl/SnapshotTransactionTest.java
@@ -147,6 +147,7 @@
 import org.apache.commons.lang3.mutable.MutableLong;
 import org.apache.commons.lang3.tuple.Pair;
 import org.assertj.core.api.Assertions;
+import org.awaitility.Awaitility;
 import org.jmock.Expectations;
 import org.jmock.Mockery;
 import org.jmock.lib.concurrent.DeterministicScheduler;
@@ -377,7 +378,12 @@ public void testImmutableTs() throws Exception {
             return t.getTimestamp();
         });
         assertThat(firstTs).isLessThan(txManager.getImmutableTimestamp());
-        assertThat(startTs).isLessThan(txManager.getImmutableTimestamp());
+
+        // Immutable timestamp may not be cleared immediately.
+        Awaitility.await("immutable timestamp should advance past our transaction's start timestamp")
+                .atMost(5, TimeUnit.SECONDS)
+                .pollInterval(10, TimeUnit.MILLISECONDS)
+                .until(() -> startTs < txManager.getImmutableTimestamp());
     }
 
     // If lock happens concurrent with get, we aren't sure that we can rollback the transaction