diff --git a/src/services/search/expressions/ancestor.js b/src/services/search/expressions/ancestor.ts
similarity index 75%
rename from src/services/search/expressions/ancestor.js
rename to src/services/search/expressions/ancestor.ts
index f48e9e59f..6f169e33a 100644
--- a/src/services/search/expressions/ancestor.js
+++ b/src/services/search/expressions/ancestor.ts
@@ -1,12 +1,19 @@
 "use strict";
 
-const Expression = require('./expression');
-const NoteSet = require('../note_set');
-const log = require('../../log');
-const becca = require('../../../becca/becca');
+import Expression = require('./expression');
+import NoteSet = require('../note_set');
+import log = require('../../log');
+import becca = require('../../../becca/becca');
+import SearchContext = require('../search_context');
 
 class AncestorExp extends Expression {
-    constructor(ancestorNoteId, ancestorDepth) {
+
+    private ancestorNoteId: string;
+    private ancestorDepthComparator;
+    
+    ancestorDepth: string;
+
+    constructor(ancestorNoteId: string, ancestorDepth: string) {
         super();
 
         this.ancestorNoteId = ancestorNoteId;
@@ -14,7 +21,7 @@ class AncestorExp extends Expression {
         this.ancestorDepthComparator = this.getComparator(ancestorDepth);
     }
 
-    execute(inputNoteSet, executionContext, searchContext) {
+    execute(inputNoteSet: NoteSet, executionContext: {}, searchContext: SearchContext) {
         const ancestorNote = becca.notes[this.ancestorNoteId];
 
         if (!ancestorNote) {
@@ -44,7 +51,7 @@ class AncestorExp extends Expression {
         return depthConformingNoteSet;
     }
 
-    getComparator(depthCondition) {
+    getComparator(depthCondition: string): ((depth: number) => boolean) | null {
         if (!depthCondition) {
             return null;
         }
diff --git a/src/services/search/expressions/expression.ts b/src/services/search/expressions/expression.ts
index a83c139f2..c74341ba2 100644
--- a/src/services/search/expressions/expression.ts
+++ b/src/services/search/expressions/expression.ts
@@ -10,12 +10,6 @@ abstract class Expression {
         this.name = this.constructor.name; // for DEBUG mode to have expression name as part of dumped JSON
     }
 
-    /**
-     * @param {NoteSet} inputNoteSet
-     * @param {object} executionContext
-     * @param {SearchContext} searchContext
-     * @returns {NoteSet}
-     */
     abstract execute(inputNoteSet: NoteSet, executionContext: {}, searchContext: SearchContext): NoteSet;
 }
 
diff --git a/src/services/search/services/parse.js b/src/services/search/services/parse.js
index 6b2e8fa84..17f0844ca 100644
--- a/src/services/search/services/parse.js
+++ b/src/services/search/services/parse.js
@@ -14,7 +14,7 @@ const LabelComparisonExp = require('../expressions/label_comparison.js');
 const NoteFlatTextExp = require('../expressions/note_flat_text.js');
 const NoteContentFulltextExp = require('../expressions/note_content_fulltext.js');
 const OrderByAndLimitExp = require('../expressions/order_by_and_limit.js');
-const AncestorExp = require('../expressions/ancestor.js');
+const AncestorExp = require('../expressions/ancestor');
 const buildComparator = require('./build_comparator.js');
 const ValueExtractor = require('../value_extractor');
 const utils = require('../../utils');