diff --git a/index/file_category.go b/index/file_category.go
index 6ca4800af..172ec4754 100644
--- a/index/file_category.go
+++ b/index/file_category.go
@@ -111,4 +111,4 @@ func decodeCategory(c byte) (FileCategory, error) {
 	default:
 		return FileCategoryMissing, errors.New("unrecognized file category")
 	}
-}
+}
\ No newline at end of file
diff --git a/index/indexdata.go b/index/indexdata.go
index 6793ec377..7ce1bc265 100644
--- a/index/indexdata.go
+++ b/index/indexdata.go
@@ -103,6 +103,9 @@ type indexData struct {
 
 	// rawConfigMasks contains the encoded RawConfig for each repository
 	rawConfigMasks []uint8
+
+	//topic
+	topic String
 }
 
 type symbolData struct {
@@ -188,6 +191,19 @@ func (d *indexData) getCategory(idx uint32) FileCategory {
 	return category
 }
 
+func (d *indexData) geTopic(idx uint32) String {
+	if len(d.topic) == 0 {
+		// So return 'Error'
+		return Error
+	}
+	
+	topic, err := decodeTopic(d.topic[idx])
+	if err != nil {
+		return None
+	}
+	return topic
+}
+
 // calculates stats for files in the range [start, end).
 func (d *indexData) calculateStatsForFileRange(start, end uint32) zoekt.RepoStats {
 	if start >= end {
diff --git a/index/matchtree.go b/index/matchtree.go
index 6929b350c..628db2b2d 100644
--- a/index/matchtree.go
+++ b/index/matchtree.go
@@ -1222,6 +1222,19 @@ func (d *indexData) newMatchTree(q query.Q, opt matchTreeOpt) (matchTree, error)
 			},
 		}, nil
 
+	case *query.topic:
+		code, ok := d.metaData.LanguageMap[s.Language]
+		if !ok {
+			return &noMatchTree{Why: "topic"}, nil
+		}
+		return &docMatchTree{
+			reason:  "topic",
+			numDocs: d.numDocs(),
+			predicate: func(docID uint32) bool {
+				return d.geTopic(docID) == code //replace getLanguage by getTopic
+			},
+		}, nil
+
 	case query.RawConfig:
 		return &docMatchTree{
 			reason:  s.String(),
diff --git a/index/toc.go b/index/toc.go
index f42887939..1cbaa01f8 100644
--- a/index/toc.go
+++ b/index/toc.go
@@ -101,6 +101,8 @@ type indexTOC struct {
 	reposIDsBitmap simpleSection
 
 	ranks simpleSection
+
+	topic simpleSection
 }
 
 func (t *indexTOC) sections() []section {
@@ -132,6 +134,7 @@ func (t *indexTOC) sections() []section {
 		&t.contentChecksums,
 		&t.languages,
 		&t.runeDocSections,
+		&t.topic,
 	}
 }
 
@@ -185,6 +188,7 @@ func (t *indexTOC) sectionsTaggedList() []taggedSection {
 		{"runeDocSections", &t.runeDocSections},
 		{"repos", &t.repos},
 		{"reposIDsBitmap", &t.reposIDsBitmap},
+		{"topic", &t.topic},
 
 		// We no longer write these sections, but we still return them here to avoid
 		// warnings about unknown sections.