diff --git a/Terminal/Source/CocoaWindow.mm b/Terminal/Source/CocoaWindow.mm
index c8def11..e3d53da 100644
--- a/Terminal/Source/CocoaWindow.mm
+++ b/Terminal/Source/CocoaWindow.mm
@@ -572,7 +572,10 @@ -(id)initWithImpl:(BearLibTerminal::CocoaWindow::Impl*)impl;
     
     void CocoaWindow::SetFullscreen(bool fullscreen)
     {
-        LOG(Error, "CocoaWindow::SetFullscreen: not yet implemented");
+        bool is_fullscreen = ([m_impl->m_window styleMask] & NSFullScreenWindowMask) == NSFullScreenWindowMask;
+        if (is_fullscreen != fullscreen) {
+            [m_impl->m_window toggleFullScreen: nil];
+        }
     }
     
     void CocoaWindow::SetCursorVisibility(bool visible)
diff --git a/Terminal/Source/Terminal.cpp b/Terminal/Source/Terminal.cpp
index e3ec9a1..62cef9d 100644
--- a/Terminal/Source/Terminal.cpp
+++ b/Terminal/Source/Terminal.cpp
@@ -655,6 +655,7 @@ namespace BearLibTerminal
 		if (updated.window_fullscreen != m_options.window_fullscreen)
 		{
 			// XXX: It's not always possible to change fullscreen state in runtime.
+			m_vars[TK_FULLSCREEN] = updated.window_fullscreen;
 			m_window->SetFullscreen(updated.window_fullscreen);
 		}