diff --git a/src/extern/kwin.d.ts b/src/extern/kwin.d.ts
index b0f87c7..7717783 100644
--- a/src/extern/kwin.d.ts
+++ b/src/extern/kwin.d.ts
@@ -22,7 +22,7 @@ declare const Workspace: {
     readonly currentActivityChanged: QSignal<[]>;
     readonly virtualScreenSizeChanged: QSignal<[]>;
 
-    clientArea(option: ClientAreaOption, output: Output, kwinDesktop: KwinDesktop);
+    clientArea(option: ClientAreaOption, output: Output, kwinDesktop: KwinDesktop): QmlRect;
 };
 
 const enum ClientAreaOption {
diff --git a/src/extern/qt.d.ts b/src/extern/qt.d.ts
index 08de3a6..cfcb536 100644
--- a/src/extern/qt.d.ts
+++ b/src/extern/qt.d.ts
@@ -1,12 +1,12 @@
 declare const console: {
-    log(...args: any[]);
-    trace();
-    assert(boolean, string?);
+    log(...args: any[]): void;
+    trace(): void;
+    assert(boolean, string?): void;
 };
 
 declare const Qt: {
     rect(x: number, y: number, width: number, height: number): QmlRect;
-    createQmlObject(qml: string, parent: QmlObject);
+    createQmlObject(qml: string, parent: QmlObject): QmlObject;
 };
 
 type QmlObject = unknown;
diff --git a/src/utils/Delayer.ts b/src/utils/Delayer.ts
index d1c160a..25be2da 100644
--- a/src/utils/Delayer.ts
+++ b/src/utils/Delayer.ts
@@ -17,7 +17,7 @@ class Delayer {
 }
 
 function initQmlTimer() {
-    return Qt.createQmlObject(
+    return <QmlTimer>Qt.createQmlObject(
         `import QtQuick 6.0
         Timer {}`,
         qmlBase
diff --git a/src/utils/ShortcutAction.ts b/src/utils/ShortcutAction.ts
index 1b06534..2787128 100644
--- a/src/utils/ShortcutAction.ts
+++ b/src/utils/ShortcutAction.ts
@@ -11,7 +11,7 @@ class ShortcutAction {
     }
 
     private static initShortcutHandler(keyBinding: KeyBinding) {
-        return Qt.createQmlObject(
+        return <ShortcutHandler>Qt.createQmlObject(
             `import QtQuick 6.0
 import org.kde.kwin 3.0
 ShortcutHandler {