diff --git a/glfw/cocoa_window.m b/glfw/cocoa_window.m
index b1c0b2b10..d94c2e30c 100644
--- a/glfw/cocoa_window.m
+++ b/glfw/cocoa_window.m
@@ -2407,6 +2407,14 @@ void _glfwPlatformSetCursor(_GLFWwindow* window, _GLFWcursor* cursor UNUSED)
         updateCursorImage(window);
 }
 
+bool _glfwPlatformIsFullscreen(_GLFWwindow* w, unsigned int flags) {
+    NSWindow *window = w->ns.object;
+    bool traditional = !(flags & 1);
+    if (traditional && @available(macOS 10.16, *)) return w->ns.in_traditional_fullscreen;
+    NSWindowStyleMask sm = [window styleMask];
+    return sm & NSWindowStyleMaskFullScreen;
+}
+
 bool _glfwPlatformToggleFullscreen(_GLFWwindow* w, unsigned int flags) {
     NSWindow *window = w->ns.object;
     bool made_fullscreen = true;
diff --git a/glfw/glfw3.h b/glfw/glfw3.h
index 3d1aafc2a..234cbd507 100644
--- a/glfw/glfw3.h
+++ b/glfw/glfw3.h
@@ -2752,6 +2752,7 @@ GLFWAPI void glfwWindowHintString(int hint, const char* value);
  */
 GLFWAPI GLFWwindow* glfwCreateWindow(int width, int height, const char* title, GLFWmonitor* monitor, GLFWwindow* share);
 GLFWAPI bool glfwToggleFullscreen(GLFWwindow *window, unsigned int flags);
+GLFWAPI bool glfwIsFullscreen(GLFWwindow *window, unsigned int flags);
 
 /*! @brief Destroys the specified window and its context.
  *
diff --git a/glfw/internal.h b/glfw/internal.h
index a14d0ffb3..12591cfba 100644
--- a/glfw/internal.h
+++ b/glfw/internal.h
@@ -717,6 +717,7 @@ void _glfwPlatformSetWindowMonitor(_GLFWwindow* window, _GLFWmonitor* monitor,
                                    int xpos, int ypos, int width, int height,
                                    int refreshRate);
 bool _glfwPlatformToggleFullscreen(_GLFWwindow *w, unsigned int flags);
+bool _glfwPlatformIsFullscreen(_GLFWwindow *w, unsigned int flags);
 int _glfwPlatformWindowFocused(_GLFWwindow* window);
 int _glfwPlatformWindowOccluded(_GLFWwindow* window);
 int _glfwPlatformWindowIconified(_GLFWwindow* window);
diff --git a/glfw/window.c b/glfw/window.c
index 9ad3add66..b69300e2b 100644
--- a/glfw/window.c
+++ b/glfw/window.c
@@ -1058,6 +1058,10 @@ GLFWAPI bool glfwToggleFullscreen(GLFWwindow* wh, unsigned int flags) {
     return false;
 }
 
+GLFWAPI bool glfwIsFullscreen(GLFWwindow* wh, unsigned int flags) {
+    return _glfwPlatformIsFullscreen((_GLFWwindow*)wh, flags);
+}
+
 GLFWAPI void glfwSetWindowUserPointer(GLFWwindow* handle, void* pointer)
 {
     _GLFWwindow* window = (_GLFWwindow*) handle;
diff --git a/glfw/wl_window.c b/glfw/wl_window.c
index 528b95458..a3c46d94d 100644
--- a/glfw/wl_window.c
+++ b/glfw/wl_window.c
@@ -413,9 +413,15 @@ static void setFullscreen(_GLFWwindow* window, _GLFWmonitor* monitor, bool on)
     setIdleInhibitor(window, on);
 }
 
+
+bool
+_glfwPlatformIsFullscreen(_GLFWwindow *window, unsigned int flags UNUSED) {
+    return window->wl.toplevel_states & TOPLEVEL_STATE_FULLSCREEN;
+}
+
 bool
 _glfwPlatformToggleFullscreen(_GLFWwindow *window, unsigned int flags UNUSED) {
-    bool already_fullscreen = window->wl.toplevel_states & TOPLEVEL_STATE_FULLSCREEN;
+    bool already_fullscreen = _glfwPlatformIsFullscreen(window, flags);
     setFullscreen(window, NULL, !already_fullscreen);
     return !already_fullscreen;
 }
diff --git a/glfw/x11_window.c b/glfw/x11_window.c
index bb46ea63f..b9528add3 100644
--- a/glfw/x11_window.c
+++ b/glfw/x11_window.c
@@ -343,6 +343,11 @@ set_fullscreen(_GLFWwindow *window, bool on) {
     }
 }
 
+bool
+_glfwPlatformIsFullscreen(_GLFWwindow *window, unsigned int flags UNUSED) {
+    return is_window_fullscreen(window);
+}
+
 bool
 _glfwPlatformToggleFullscreen(_GLFWwindow *window, unsigned int flags UNUSED) {
     bool already_fullscreen = is_window_fullscreen(window);
diff --git a/kitty/glfw.c b/kitty/glfw.c
index 8bf320da8..1adc5863f 100644
--- a/kitty/glfw.c
+++ b/kitty/glfw.c
@@ -592,7 +592,9 @@ static bool
 toggle_fullscreen_for_os_window(OSWindow *w) {
     if (w && w->handle) {
 #ifdef __APPLE__
-        if (!OPT(macos_traditional_fullscreen)) return glfwToggleFullscreen(w->handle, 1);
+        if (!OPT(macos_traditional_fullscreen)) {
+            return glfwToggleFullscreen(w->handle, 1);
+        }
 #endif
         return do_toggle_fullscreen(w);
     }