diff --git a/src/win32/base_sysfb.cpp b/src/win32/base_sysfb.cpp
index 8324c250f..6e90ca81c 100644
--- a/src/win32/base_sysfb.cpp
+++ b/src/win32/base_sysfb.cpp
@@ -71,7 +71,6 @@ EXTERN_CVAR(Int, vid_defheight)
 //
 //==========================================================================
 
-
 //==========================================================================
 //
 // 
@@ -278,14 +277,14 @@ void SystemBaseFrameBuffer::SetWindowSize(int w, int h)
 //
 //==========================================================================
 
-void SystemBaseFrameBuffer::PositionWindow(bool fullscreen)
+void SystemBaseFrameBuffer::PositionWindow(bool fullscreen, bool initialcall)
 {
 	RECT r;
 	LONG style, exStyle;
 
 	RECT monRect;
 
-	if (!m_Fullscreen && fullscreen) SaveWindowedPos();
+	if (!m_Fullscreen && fullscreen && !initialcall) SaveWindowedPos();
 	if (m_Monitor)
 	{
 		MONITORINFOEX mi;
@@ -296,6 +295,13 @@ void SystemBaseFrameBuffer::PositionWindow(bool fullscreen)
 			strcpy(m_displayDeviceNameBuffer, mi.szDevice);
 			m_displayDeviceName = m_displayDeviceNameBuffer;
 			monRect = mi.rcMonitor;
+
+			// Set the default windowed size if not specified yet.
+			if (win_w < 0 || win_h < 0)
+			{
+				win_w = int(monRect.right - monRect.left) * 8 / 10;
+				win_h = int(monRect.bottom - monRect.top) * 8 / 10;
+			}
 		}
 	}
 
@@ -347,7 +353,7 @@ SystemBaseFrameBuffer::SystemBaseFrameBuffer(void *hMonitor, bool fullscreen) :
 {
 	m_Monitor = hMonitor;
 	m_displayDeviceName = 0;
-	PositionWindow(fullscreen);
+	PositionWindow(fullscreen, true);
 
 	HDC hDC = GetDC(Window);
 
diff --git a/src/win32/base_sysfb.h b/src/win32/base_sysfb.h
index 84eb5c981..6d7470cef 100644
--- a/src/win32/base_sysfb.h
+++ b/src/win32/base_sysfb.h
@@ -10,7 +10,7 @@ class SystemBaseFrameBuffer : public DFrameBuffer
 	void RestoreWindowedPos();
 
 public:
-	SystemBaseFrameBuffer() {}
+	SystemBaseFrameBuffer();
 	// Actually, hMonitor is a HMONITOR, but it's passed as a void * as there
     // look to be some cross-platform bits in the way.
 	SystemBaseFrameBuffer(void *hMonitor, bool fullscreen);
@@ -28,7 +28,7 @@ protected:
 	void GetCenteredPos(int in_w, int in_h, int &winx, int &winy, int &winw, int &winh, int &scrwidth, int &scrheight);
 	void KeepWindowOnScreen(int &winx, int &winy, int winw, int winh, int scrwidth, int scrheight);
 
-	void PositionWindow(bool fullscreen);
+	void PositionWindow(bool fullscreen, bool initialcall = false);
 
 	void ResetGammaTable();
 	void SetGammaTable(uint16_t * tbl);