diff --git a/package.json b/package.json
index e182391..9de3482 100644
--- a/package.json
+++ b/package.json
@@ -7,7 +7,7 @@
     },
     "publisher": "eamodio",
     "engines": {
-        "vscode": "^1.18.0"
+        "vscode": "^1.19.0"
     },
     "license": "SEE LICENSE IN LICENSE",
     "displayName": "Git Lens \u2014 git blame annotations, code lens, and more",
diff --git a/src/activeEditorTracker.ts b/src/activeEditorTracker.ts
index e8c598f..ee0fa25 100644
--- a/src/activeEditorTracker.ts
+++ b/src/activeEditorTracker.ts
@@ -12,7 +12,7 @@ export class ActiveEditorTracker extends Disposable {
     constructor() {
         super(() => this.dispose());
 
-        const fn = Functions.debounce((e: TextEditor) => this._resolver && this._resolver(e), 50);
+        const fn = Functions.debounce((e: TextEditor | undefined) => this._resolver && this._resolver(e), 50);
         this._disposable = window.onDidChangeActiveTextEditor(fn);
     }