diff --git a/src/main/java/com/googlesource/gerrit/plugins/spannerrefdb/Lock.java b/src/main/java/com/googlesource/gerrit/plugins/spannerrefdb/Lock.java
index 20a921b..dd01966 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/spannerrefdb/Lock.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/spannerrefdb/Lock.java
@@ -138,7 +138,6 @@
               Struct row =
                   transaction.readRow(
                       "locks", Key.of(projectName, refName), Arrays.asList("token", "heartbeat"));
-
               if (row == null) {
                 // If the old lock doesn't exist any more, we create a new one
                 transaction.buffer(createLock());
@@ -155,7 +154,7 @@
                           .bind("ref")
                           .to(refName)
                           .build());
-              if (resultSet.getLong("seconds") <= SECONDS_FOR_STALE_HEARTBEAT) {
+              if (resultSet.next() && resultSet.getLong("seconds") <= SECONDS_FOR_STALE_HEARTBEAT) {
                 // Check if the old lock is stale; if not, do nothing
                 return false;
               }
diff --git a/src/test/java/com/googlesource/gerrit/plugins/spannerrefdb/EmulatedSpannerRefDb.java b/src/test/java/com/googlesource/gerrit/plugins/spannerrefdb/EmulatedSpannerRefDb.java
index 70adc77..4ed2b90 100644
--- a/src/test/java/com/googlesource/gerrit/plugins/spannerrefdb/EmulatedSpannerRefDb.java
+++ b/src/test/java/com/googlesource/gerrit/plugins/spannerrefdb/EmulatedSpannerRefDb.java
@@ -114,6 +114,10 @@
     return spannerRefDb;
   }
 
+  public DatabaseClient getDatabaseClient() {
+    return databaseClient;
+  }
+
   private SpannerOptions getEmulatorOptions() {
     return SpannerOptions.newBuilder()
         .setEmulatorHost(container.getEmulatorGrpcEndpoint())
diff --git a/src/test/java/com/googlesource/gerrit/plugins/spannerrefdb/LockTest.java b/src/test/java/com/googlesource/gerrit/plugins/spannerrefdb/LockTest.java
new file mode 100644
index 0000000..cd5d65c
--- /dev/null
+++ b/src/test/java/com/googlesource/gerrit/plugins/spannerrefdb/LockTest.java
@@ -0,0 +1,147 @@
+// Copyright (C) 2023 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.googlesource.gerrit.plugins.spannerrefdb;
+
+import static com.google.common.truth.Truth.assertThat;
+import static com.google.gerrit.testing.GerritJUnit.assertThrows;
+
+import com.gerritforge.gerrit.globalrefdb.GlobalRefDbLockException;
+import com.google.cloud.Timestamp;
+import com.google.cloud.spanner.DatabaseClient;
+import com.google.cloud.spanner.Key;
+import com.google.cloud.spanner.Mutation;
+import com.google.cloud.spanner.Struct;
+import com.google.gerrit.entities.Project;
+import java.util.Arrays;
+import java.util.Collections;
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+
+public class LockTest implements RefFixture {
+  private EmulatedSpannerRefDb emulator;
+  private SpannerRefDatabase refDb;
+  private DatabaseClient dbClient;
+
+  private String TOKEN = "token";
+  private String HEARTBEAT = "heartbeat";
+
+  @Before
+  public void setUp() throws Exception {
+    emulator = new EmulatedSpannerRefDb();
+    refDb = emulator.getSpannerRefDatabase();
+    dbClient = emulator.getDatabaseClient();
+  }
+
+  @After
+  public void tearDown() {
+    emulator.cleanup();
+  }
+
+  @Test
+  public void lockUnlockedRef_Success() throws Exception {
+    try (AutoCloseable refLock = refDb.lockRef(PROJECT_NAME_KEY, REF_NAME)) {
+      assertThat(getLockTimestamp(PROJECT_NAME_KEY, REF_NAME, TOKEN)).isNotNull();
+
+      Timestamp heartbeat = getLockTimestamp(PROJECT_NAME_KEY, REF_NAME, HEARTBEAT);
+      try {
+        Thread.sleep(4_000);
+      } catch (InterruptedException ie) {
+        Thread.currentThread().interrupt();
+      }
+      assertThat(getLockTimestamp(PROJECT_NAME_KEY, REF_NAME, HEARTBEAT).compareTo(heartbeat))
+          .isGreaterThan(0);
+    }
+
+    assertThat(getLockRow(PROJECT_NAME_KEY, REF_NAME)).isNull();
+  }
+
+  @Test
+  public void lockAlreadyLockedRef_Rejected() throws Exception {
+    try (AutoCloseable refLock = refDb.lockRef(PROJECT_NAME_KEY, REF_NAME)) {
+      GlobalRefDbLockException e =
+          assertThrows(
+              GlobalRefDbLockException.class, () -> refDb.lockRef(PROJECT_NAME_KEY, REF_NAME));
+      assertThat(e)
+          .hasMessageThat()
+          .contains(
+              String.format("Unable to lock ref %s on project %s", REF_NAME, PROJECT_NAME_KEY));
+    }
+  }
+
+  @Test
+  public void lockReleasedRef_Success() throws Exception {
+    Timestamp lockToken;
+    try (AutoCloseable refLock = refDb.lockRef(PROJECT_NAME_KEY, REF_NAME)) {
+      lockToken = getLockTimestamp(PROJECT_NAME_KEY, REF_NAME, TOKEN);
+    }
+
+    try (AutoCloseable refLock = refDb.lockRef(PROJECT_NAME_KEY, REF_NAME)) {
+      Timestamp newLockToken = getLockTimestamp(PROJECT_NAME_KEY, REF_NAME, TOKEN);
+      assertThat(lockToken).isNotEqualTo(newLockToken);
+    }
+  }
+
+  @Test
+  public void reclaimStaleLockedRef_Success() throws Exception {
+    Timestamp staleTimestamp = Timestamp.ofTimeSecondsAndNanos(0, 0);
+    insertLockRow(staleTimestamp);
+    try (AutoCloseable refLock = refDb.lockRef(PROJECT_NAME_KEY, REF_NAME)) {
+      Timestamp newLockToken = getLockTimestamp(PROJECT_NAME_KEY, REF_NAME, TOKEN);
+      assertThat(newLockToken).isNotNull();
+      assertThat(staleTimestamp.compareTo(newLockToken)).isLessThan(0);
+    }
+  }
+
+  @Test
+  public void reclaimFreshLockedRef_Rejected() throws Exception {
+    Timestamp freshTimestamp = Timestamp.now();
+    insertLockRow(freshTimestamp);
+    GlobalRefDbLockException e =
+        assertThrows(
+            GlobalRefDbLockException.class, () -> refDb.lockRef(PROJECT_NAME_KEY, REF_NAME));
+    assertThat(e)
+        .hasMessageThat()
+        .contains(String.format("Unable to lock ref %s on project %s", REF_NAME, PROJECT_NAME_KEY));
+  }
+
+  private Timestamp getLockTimestamp(Project.NameKey project, String refName, String column) {
+    Struct row = getLockRow(project, refName);
+    return row != null ? row.getTimestamp(column) : null;
+  }
+
+  private Struct getLockRow(Project.NameKey project, String refName) {
+    return dbClient
+        .singleUse()
+        .readRow("locks", Key.of(project.get(), refName), Arrays.asList(TOKEN, HEARTBEAT));
+  }
+
+  private void insertLockRow(Timestamp timestamp) {
+    Mutation staleLock =
+        Mutation.newInsertBuilder("locks")
+            .set("project")
+            .to(PROJECT_NAME_KEY.get())
+            .set("ref")
+            .to(REF_NAME)
+            .set("heartbeat")
+            .to(timestamp)
+            .set("token")
+            .to(timestamp)
+            .set("owner")
+            .to("")
+            .build();
+    dbClient.write(Collections.singletonList(staleLock));
+  }
+}