diff --git a/inc/main.h b/inc/main.h
index a40daa1..28a3378 100644
--- a/inc/main.h
+++ b/inc/main.h
@@ -73,6 +73,8 @@ typedef struct IDirectDrawImpl
         DEVMODE mode;
         struct { int width; int height; int x; int y; } viewport;
 
+        LONG paletteUpdated;
+        LONG surfaceUpdated;
     } render;
 
     HWND hWnd;
diff --git a/src/palette.c b/src/palette.c
index d7e6bd5..fb965b2 100644
--- a/src/palette.c
+++ b/src/palette.c
@@ -62,6 +62,7 @@ HRESULT __stdcall ddraw_palette_SetEntries(IDirectDrawPaletteImpl *This, DWORD d
     /* FIXME: only refresh the screen when the primary palette is changed */
     if(ddraw->primary && ddraw->render.run)
     {
+        InterlockedExchange(&ddraw->render.paletteUpdated, TRUE);
         ReleaseSemaphore(ddraw->render.sem, 1, NULL);
     }
 
diff --git a/src/render.c b/src/render.c
index b0f1fbe..5cee066 100644
--- a/src/render.c
+++ b/src/render.c
@@ -477,10 +477,18 @@ DWORD WINAPI render_main(void)
             if (paletteConvProgram)
             {
                 glBindTexture(GL_TEXTURE_2D, paletteTexId);
-                glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, 256, 1, GL_RGBA, GL_UNSIGNED_BYTE, ddraw->primary->palette->data_bgr);
+                if (InterlockedExchange(&ddraw->render.paletteUpdated, FALSE))
+                {
+                    glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, 256, 1, GL_RGBA, GL_UNSIGNED_BYTE,
+                        ddraw->primary->palette->data_bgr);
+                }
 
                 glBindTexture(GL_TEXTURE_2D, surfaceTexId);
-                glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, ddraw->width, ddraw->height, surfaceFormat, GL_UNSIGNED_BYTE, ddraw->primary->surface);
+                if (InterlockedExchange(&ddraw->render.surfaceUpdated, FALSE))
+                {
+                    glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, ddraw->width, ddraw->height, surfaceFormat, GL_UNSIGNED_BYTE,
+                        ddraw->primary->surface);
+                }
             }
             else
             {
diff --git a/src/surface.c b/src/surface.c
index a917536..569fa17 100644
--- a/src/surface.c
+++ b/src/surface.c
@@ -107,11 +107,12 @@ HRESULT __stdcall ddraw_surface_Blt(IDirectDrawSurfaceImpl *This, LPRECT lpDestR
         int dst_w = lpDestRect->right - lpDestRect->left;
         int dst_h = lpDestRect->bottom - lpDestRect->top;
 
-        for (int y = 0; y < dst_h; y++)
+        int y, x;
+        for (y = 0; y < dst_h; y++)
         {
             int ydst = This->width * (y + lpDestRect->top);
 
-            for (int x = 0; x < dst_w; x++)
+            for (x = 0; x < dst_w; x++)
             {
                 ((unsigned char *)This->surface)[x + lpDestRect->left + ydst] = lpDDBltFx->dwFillColor;
             }
@@ -169,6 +170,7 @@ HRESULT __stdcall ddraw_surface_Blt(IDirectDrawSurfaceImpl *This, LPRECT lpDestR
 
     if(This->caps & DDSCAPS_PRIMARYSURFACE && !(This->flags & DDSD_BACKBUFFERCOUNT) && ddraw->render.run)
     {
+        InterlockedExchange(&ddraw->render.surfaceUpdated, TRUE);
         ReleaseSemaphore(ddraw->render.sem, 1, NULL);
         if (ddraw->renderer != render_main)
         {
@@ -255,6 +257,7 @@ HRESULT __stdcall ddraw_surface_Flip(IDirectDrawSurfaceImpl *This, LPDIRECTDRAWS
 
     if(This->caps & DDSCAPS_PRIMARYSURFACE && ddraw->render.run)
     {
+        InterlockedExchange(&ddraw->render.surfaceUpdated, TRUE);
         ReleaseSemaphore(ddraw->render.sem, 1, NULL);
         if (ddraw->renderer != render_main)
         {
@@ -430,6 +433,7 @@ HRESULT __stdcall ddraw_surface_Unlock(IDirectDrawSurfaceImpl *This, LPVOID lpRe
     
     if(This->caps & DDSCAPS_PRIMARYSURFACE && !(This->flags & DDSD_BACKBUFFERCOUNT) && ddraw->render.run)
     {
+        InterlockedExchange(&ddraw->render.surfaceUpdated, TRUE);
         ReleaseSemaphore(ddraw->render.sem, 1, NULL);
     }