diff --git a/atlasdb-config/src/main/java/com/palantir/atlasdb/factory/TransactionManagers.java b/atlasdb-config/src/main/java/com/palantir/atlasdb/factory/TransactionManagers.java
index 9df0b53032a..871869ad1d2 100644
--- a/atlasdb-config/src/main/java/com/palantir/atlasdb/factory/TransactionManagers.java
+++ b/atlasdb-config/src/main/java/com/palantir/atlasdb/factory/TransactionManagers.java
@@ -336,6 +336,7 @@ private static TransactionManager createInMemory(
                 .globalMetricsRegistry(new MetricRegistry())
                 .globalTaggedMetricRegistry(DefaultTaggedMetricRegistry.getDefault())
                 .lockAndTimestampServiceFactory(maybeFactory)
+                .defaultTimelockClientFactory((service, _management) -> TimeLockClient.withSynchronousUnlocker(service))
                 .addAllSchemas(schemas)
                 .build()
                 .serializable();
diff --git a/atlasdb-tests-shared/src/test/java/com/palantir/atlasdb/factory/TransactionManagersTest.java b/atlasdb-tests-shared/src/test/java/com/palantir/atlasdb/factory/TransactionManagersTest.java
index 5363f97e493..aac9c587600 100644
--- a/atlasdb-tests-shared/src/test/java/com/palantir/atlasdb/factory/TransactionManagersTest.java
+++ b/atlasdb-tests-shared/src/test/java/com/palantir/atlasdb/factory/TransactionManagersTest.java
@@ -60,6 +60,9 @@
 import com.palantir.atlasdb.sweep.queue.config.ImmutableTargetedSweepInstallConfig;
 import com.palantir.atlasdb.sweep.queue.config.ImmutableTargetedSweepRuntimeConfig;
 import com.palantir.atlasdb.table.description.GenericTestSchema;
+import com.palantir.atlasdb.table.description.generated.GenericTestSchemaTableFactory;
+import com.palantir.atlasdb.table.description.generated.RangeScanTestTable;
+import com.palantir.atlasdb.table.description.generated.RangeScanTestTable.RangeScanTestRow;
 import com.palantir.atlasdb.timelock.adjudicate.feedback.TimeLockClientFeedbackService;
 import com.palantir.atlasdb.transaction.ImmutableTransactionConfig;
 import com.palantir.atlasdb.transaction.TransactionConfig;
@@ -684,6 +687,22 @@ public void sanityCheckFeedbackReportingPipeline() {
         verifyFeedbackIsReportedToService();
     }
 
+    @Test
+    public void inMemoryUsesSynchronousUnlocker() {
+        TransactionManager transactionManager = TransactionManagers.createInMemory(GenericTestSchema.getSchema());
+        for (int i = 0; i < 100; i++) {
+            long immutableTimestamp = transactionManager.getImmutableTimestamp();
+            long txnTimestamp = transactionManager.runTaskWithRetry(txn -> {
+                assertThat(txn.getTimestamp()).isGreaterThan(immutableTimestamp);
+                assertThat(transactionManager.getImmutableTimestamp()).isGreaterThanOrEqualTo(immutableTimestamp);
+                RangeScanTestTable table = GenericTestSchemaTableFactory.of().getRangeScanTestTable(txn);
+                table.putColumn1(RangeScanTestRow.of("hello"), 1L);
+                return txn.getTimestamp();
+            });
+            assertThat(transactionManager.getImmutableTimestamp()).isGreaterThan(txnTimestamp);
+        }
+    }
+
     private void setUpTimeLockConfig() {
         timeLockRuntimeConfig = getTimelockRuntimeConfig(ImmutableList.of(getUriForPort(availablePort)));
         when(mockAtlasDbRuntimeConfig.timelockRuntime()).thenReturn(Optional.of(timeLockRuntimeConfig));
diff --git a/changelog/@unreleased/pr-7309.v2.yml b/changelog/@unreleased/pr-7309.v2.yml
new file mode 100644
index 00000000000..73f03828529
--- /dev/null
+++ b/changelog/@unreleased/pr-7309.v2.yml
@@ -0,0 +1,5 @@
+type: improvement
+improvement:
+  description: TransactionManagers#createInMemory uses synchronous unlocker.
+  links:
+  - https://github.com/palantir/atlasdb/pull/7309