diff --git a/opengrok-indexer/src/main/java/org/opengrok/indexer/history/Repository.java b/opengrok-indexer/src/main/java/org/opengrok/indexer/history/Repository.java
index f7584add142..d2ddf2831f2 100644
--- a/opengrok-indexer/src/main/java/org/opengrok/indexer/history/Repository.java
+++ b/opengrok-indexer/src/main/java/org/opengrok/indexer/history/Repository.java
@@ -18,7 +18,7 @@
  */
 
 /*
- * Copyright (c) 2008, 2023, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2008, 2024, Oracle and/or its affiliates. All rights reserved.
  * Portions Copyright (c) 2017, 2020, Chris Fraire <cfraire@me.com>.
  */
 package org.opengrok.indexer.history;
@@ -283,7 +283,7 @@ boolean hasFileBasedTags() {
         return false;
     }
 
-    NavigableSet<TagEntry> getTagList() {
+    @Nullable NavigableSet<TagEntry> getTagList() {
         return this.tagList;
     }
 
diff --git a/opengrok-indexer/src/test/java/org/opengrok/indexer/history/MercurialRepositoryTest.java b/opengrok-indexer/src/test/java/org/opengrok/indexer/history/MercurialRepositoryTest.java
index 4654e7d4b8f..11a3e4470a3 100644
--- a/opengrok-indexer/src/test/java/org/opengrok/indexer/history/MercurialRepositoryTest.java
+++ b/opengrok-indexer/src/test/java/org/opengrok/indexer/history/MercurialRepositoryTest.java
@@ -31,19 +31,27 @@
 import org.junit.jupiter.params.provider.MethodSource;
 import org.junit.jupiter.params.provider.ValueSource;
 import org.opengrok.indexer.condition.EnabledForRepository;
+import org.opengrok.indexer.configuration.CommandTimeoutType;
 import org.opengrok.indexer.configuration.RuntimeEnvironment;
 import org.opengrok.indexer.util.Executor;
+import org.opengrok.indexer.util.IOUtils;
 import org.opengrok.indexer.util.TestRepository;
 
 import java.io.File;
 import java.io.IOException;
 import java.io.InputStream;
 import java.net.URISyntaxException;
+import java.nio.file.Files;
+import java.nio.file.Path;
 import java.nio.file.Paths;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
+import java.util.Date;
 import java.util.List;
+import java.util.Objects;
+import java.util.Set;
+import java.util.TreeSet;
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
 
@@ -97,7 +105,7 @@ public class MercurialRepositoryTest {
      */
     private void setUpTestRepository() throws IOException, URISyntaxException {
         repository = new TestRepository();
-        repository.create(getClass().getResource("/repositories"));
+        repository.create(Objects.requireNonNull(getClass().getResource("/repositories")));
         repositoryRoot = new File(repository.getSourceRoot(), "mercurial");
     }
 
@@ -441,4 +449,31 @@ void testAnnotationPositive(Pair<String, List<String>> pair) throws Exception {
         List<String> revisions = new ArrayList<>(annotation.getRevisions());
         assertEquals(pair.getValue(), revisions);
     }
+
+    @Test
+    void testBuildTagListEmpty() throws Exception {
+        Path repositoryRootPath = Files.createDirectory(Path.of(RuntimeEnvironment.getInstance().getSourceRootPath(),
+                "emptyTagsTest"));
+        File repositoryRoot = repositoryRootPath.toFile();
+        assertTrue(repositoryRoot.isDirectory());
+        runHgCommand(repositoryRoot, "init");
+        MercurialRepository hgRepo = (MercurialRepository) RepositoryFactory.getRepository(repositoryRoot);
+        assertNotNull(hgRepo);
+        hgRepo.buildTagList(new File(hgRepo.getDirectoryName()), CommandTimeoutType.INDEXER);
+        assertEquals(0, hgRepo.getTagList().size());
+        IOUtils.removeRecursive(repositoryRootPath);
+    }
+
+    @Test
+    void testBuildTagListInitial() throws Exception {
+        MercurialRepository hgRepo = (MercurialRepository) RepositoryFactory.getRepository(repositoryRoot);
+        assertNotNull(hgRepo);
+        hgRepo.buildTagList(new File(hgRepo.getDirectoryName()), CommandTimeoutType.INDEXER);
+        var tags = hgRepo.getTagList();
+        assertEquals(1, tags.size());
+        Set<TagEntry> expectedTags = new TreeSet<>();
+        TagEntry tagEntry = new MercurialTagEntry(7, "start_of_novel");
+        expectedTags.add(tagEntry);
+        assertEquals(expectedTags, tags);
+    }
 }