diff --git a/src/gui/render/renderDX9.h b/src/gui/render/renderDX9.h
index c7cd4e1e5..e9a8bef25 100644
--- a/src/gui/render/renderDX9.h
+++ b/src/gui/render/renderDX9.h
@@ -47,6 +47,7 @@ class FurnaceGUIRenderDX9: public FurnaceGUIRender {
     float getTextureU(FurnaceGUITexture* which);
     float getTextureV(FurnaceGUITexture* which);
     FurnaceGUITextureFormat getTextureFormat(FurnaceGUITexture* which);
+    bool isTextureValid(FurnaceGUITexture* which);
     bool lockTexture(FurnaceGUITexture* which, void** data, int* pitch);
     bool unlockTexture(FurnaceGUITexture* which);
     bool updateTexture(FurnaceGUITexture* which, void* data, int pitch);