diff --git a/src/domain/ViewModel.js b/src/domain/ViewModel.js
index dc7b1f36..cccdb847 100644
--- a/src/domain/ViewModel.js
+++ b/src/domain/ViewModel.js
@@ -45,6 +45,7 @@ export class ViewModel extends EventEmitter {
         if (this.disposables) {
             return this.disposables.untrack(disposable);
         }
+        return null;
     }
 
     dispose() {
diff --git a/src/utils/Disposables.js b/src/utils/Disposables.js
index f682bc08..8bb24843 100644
--- a/src/utils/Disposables.js
+++ b/src/utils/Disposables.js
@@ -47,6 +47,7 @@ export class Disposables {
         if (idx >= 0) {
             this._disposables.splice(idx, 1);
         }
+        return null;
     }
 
     dispose() {