diff --git a/ui/platform/linux/ui_utility_linux.h b/ui/platform/linux/ui_utility_linux.h
index c6be70e..d03c657 100644
--- a/ui/platform/linux/ui_utility_linux.h
+++ b/ui/platform/linux/ui_utility_linux.h
@@ -32,6 +32,9 @@ inline void ShowOverAll(not_null<QWidget*> widget, bool canFocus) {
 inline void BringToBack(not_null<QWidget*> widget) {
 }
 
+inline void DisableSystemWindowResize(not_null<QWidget*> widget, QSize ratio) {
+}
+
 inline constexpr bool UseMainQueueGeneric() {
 	return true;
 }
diff --git a/ui/platform/mac/ui_utility_mac.mm b/ui/platform/mac/ui_utility_mac.mm
index b230169..1948349 100644
--- a/ui/platform/mac/ui_utility_mac.mm
+++ b/ui/platform/mac/ui_utility_mac.mm
@@ -91,6 +91,15 @@ void DrainMainQueue() {
 void IgnoreAllActivation(not_null<QWidget*> widget) {
 }
 
+void DisableSystemWindowResize(not_null<QWidget*> widget, QSize ratio) {
+	const auto winId = widget->window()->winId();
+	if (const auto view = reinterpret_cast<NSView*>(winId)) {
+		if (const auto window = [view window]) {
+			window.styleMask &= ~NSWindowStyleMaskResizable;
+		}
+	}
+}
+
 std::optional<bool> IsOverlapped(
 		not_null<QWidget*> widget,
 		const QRect &rect) {
diff --git a/ui/platform/ui_platform_utility.h b/ui/platform/ui_platform_utility.h
index c0bb5ea..4452332 100644
--- a/ui/platform/ui_platform_utility.h
+++ b/ui/platform/ui_platform_utility.h
@@ -29,6 +29,8 @@ void BringToBack(not_null<QWidget*> widget);
 void IgnoreAllActivation(not_null<QWidget*> widget);
 void ClearTransientParent(not_null<QWidget*> widget);
 
+void DisableSystemWindowResize(not_null<QWidget*> widget, QSize ratio);
+
 [[nodiscard]] std::optional<bool> IsOverlapped(
     not_null<QWidget*> widget,
     const QRect &rect);
diff --git a/ui/platform/win/ui_utility_win.h b/ui/platform/win/ui_utility_win.h
index 2870cd0..67d8d89 100644
--- a/ui/platform/win/ui_utility_win.h
+++ b/ui/platform/win/ui_utility_win.h
@@ -38,6 +38,9 @@ inline void BringToBack(not_null<QWidget*> widget) {
 inline void ClearTransientParent(not_null<QWidget*> widget) {
 }
 
+inline void DisableSystemWindowResize(not_null<QWidget*> widget, QSize ratio) {
+}
+
 inline constexpr bool UseMainQueueGeneric() {
 	return true;
 }