diff --git a/src/services/search/expressions/not.js b/src/services/search/expressions/not.js
deleted file mode 100644
index 3117b4a01..000000000
--- a/src/services/search/expressions/not.js
+++ /dev/null
@@ -1,19 +0,0 @@
-"use strict";
-
-const Expression = require('./expression');
-
-class NotExp extends Expression {
-    constructor(subExpression) {
-        super();
-
-        this.subExpression = subExpression;
-    }
-
-    execute(inputNoteSet, executionContext, searchContext) {
-        const subNoteSet = this.subExpression.execute(inputNoteSet, executionContext, searchContext);
-
-        return inputNoteSet.minus(subNoteSet);
-    }
-}
-
-module.exports = NotExp;
diff --git a/src/services/search/expressions/not.ts b/src/services/search/expressions/not.ts
new file mode 100644
index 000000000..e1b31c84e
--- /dev/null
+++ b/src/services/search/expressions/not.ts
@@ -0,0 +1,23 @@
+"use strict";
+
+import NoteSet = require('../note_set');
+import SearchContext = require('../search_context');
+import Expression = require('./expression');
+
+class NotExp extends Expression {
+    private subExpression: Expression;
+
+    constructor(subExpression: Expression) {
+        super();
+
+        this.subExpression = subExpression;
+    }
+
+    execute(inputNoteSet: NoteSet, executionContext: {}, searchContext: SearchContext) {
+        const subNoteSet = this.subExpression.execute(inputNoteSet, executionContext, searchContext);
+
+        return inputNoteSet.minus(subNoteSet);
+    }
+}
+
+export = NotExp;
diff --git a/src/services/search/services/parse.js b/src/services/search/services/parse.js
index e50034a93..38a022a21 100644
--- a/src/services/search/services/parse.js
+++ b/src/services/search/services/parse.js
@@ -3,7 +3,7 @@
 const dayjs = require("dayjs");
 const AndExp = require('../expressions/and');
 const OrExp = require('../expressions/or.js');
-const NotExp = require('../expressions/not.js');
+const NotExp = require('../expressions/not');
 const ChildOfExp = require('../expressions/child_of');
 const DescendantOfExp = require('../expressions/descendant_of');
 const ParentOfExp = require('../expressions/parent_of.js');