diff --git a/Easydict/Feature/Utility/EZCategory/NSViewController+EZWindow.h b/Easydict/Feature/Utility/EZCategory/NSViewController+EZWindow.h
index de32711b0..9890d7b89 100644
--- a/Easydict/Feature/Utility/EZCategory/NSViewController+EZWindow.h
+++ b/Easydict/Feature/Utility/EZCategory/NSViewController+EZWindow.h
@@ -12,7 +12,7 @@ NS_ASSUME_NONNULL_BEGIN
 
 @interface NSViewController (EZWindow)
 
-- (NSWindow *)window;
+- (nullable NSWindow *)window;
 
 @end
 
diff --git a/Easydict/Feature/Utility/EZCategory/NSViewController+EZWindow.m b/Easydict/Feature/Utility/EZCategory/NSViewController+EZWindow.m
index a73e9e2aa..a46341981 100644
--- a/Easydict/Feature/Utility/EZCategory/NSViewController+EZWindow.m
+++ b/Easydict/Feature/Utility/EZCategory/NSViewController+EZWindow.m
@@ -10,7 +10,7 @@
 
 @implementation NSViewController (EZWindow)
 
-- (NSWindow *)window {
+- (nullable NSWindow *)window {
     NSResponder *responder = self;
     while ((responder = [responder nextResponder])) {
         if ([responder isKindOfClass:[NSWindow class]]) {