diff --git a/DDrawCompat/DDraw/DirectDraw.cpp b/DDrawCompat/DDraw/DirectDraw.cpp
index a04ff04..f53cad4 100644
--- a/DDrawCompat/DDraw/DirectDraw.cpp
+++ b/DDrawCompat/DDraw/DirectDraw.cpp
@@ -149,6 +149,10 @@ namespace
 				if (wasFullscreen != isFullscreen)
 				{
 					tagSurface->setFullscreenWindow(isFullscreen ? hWnd : nullptr);
+					if (!isFullscreen)
+					{
+						DDraw::PrimarySurface::setWindowedCooperativeLevel();
+					}
 				}
 			}
 		}
diff --git a/DDrawCompat/DDraw/Surfaces/PrimarySurface.cpp b/DDrawCompat/DDraw/Surfaces/PrimarySurface.cpp
index 02215bf..da1835a 100644
--- a/DDrawCompat/DDraw/Surfaces/PrimarySurface.cpp
+++ b/DDrawCompat/DDraw/Surfaces/PrimarySurface.cpp
@@ -299,6 +299,29 @@ namespace DDraw
 		}
 	}
 
+	void PrimarySurface::setWindowedCooperativeLevel()
+	{
+		LOG_FUNC("PrimarySurface::setWindowedCooperativeLevel");
+		if (!g_primarySurface)
+		{
+			return;
+		}
+
+		RealPrimarySurface::restore();
+
+		if (FAILED(g_primarySurface->IsLost(g_primarySurface)))
+		{
+			return;
+		}
+
+		auto surface = Surface::getSurface(*g_primarySurface);
+		if (surface)
+		{
+			onLost();
+			surface->restore();
+		}
+	}
+
 	void PrimarySurface::updateFrontResource()
 	{
 		g_frontResource = DirectDrawSurface::getDriverResourceHandle(*g_primarySurface);
diff --git a/DDrawCompat/DDraw/Surfaces/PrimarySurface.h b/DDrawCompat/DDraw/Surfaces/PrimarySurface.h
index 5809af1..e825b22 100644
--- a/DDrawCompat/DDraw/Surfaces/PrimarySurface.h
+++ b/DDrawCompat/DDraw/Surfaces/PrimarySurface.h
@@ -29,6 +29,7 @@ namespace DDraw
 		static DWORD getOrigCaps();
 		static void onLost();
 		static void setAsRenderTarget();
+		static void setWindowedCooperativeLevel();
 		static void updatePalette();
 
 		template <typename TSurface>
diff --git a/DDrawCompat/DDraw/Surfaces/PrimarySurfaceImpl.cpp b/DDrawCompat/DDraw/Surfaces/PrimarySurfaceImpl.cpp
index eb74025..826339a 100644
--- a/DDrawCompat/DDraw/Surfaces/PrimarySurfaceImpl.cpp
+++ b/DDrawCompat/DDraw/Surfaces/PrimarySurfaceImpl.cpp
@@ -153,6 +153,11 @@ namespace DDraw
 	template <typename TSurface>
 	HRESULT PrimarySurfaceImpl<TSurface>::Flip(TSurface* This, TSurface* lpDDSurfaceTargetOverride, DWORD dwFlags)
 	{
+		if (!RealPrimarySurface::isFullscreen())
+		{
+			return DDERR_NOEXCLUSIVEMODE;
+		}
+
 		RealPrimarySurface::setUpdateReady();
 		RealPrimarySurface::flush();
 		RealPrimarySurface::waitForFlip(m_data->getDDS());