diff --git a/include/SDL_surface.h b/include/SDL_surface.h
index 4062012df..e18153a69 100644
--- a/include/SDL_surface.h
+++ b/include/SDL_surface.h
@@ -357,7 +357,7 @@ extern DECLSPEC void SDLCALL SDL_GetClipRect(SDL_Surface * surface,
  *  surface.
  */
 extern DECLSPEC SDL_Surface *SDLCALL SDL_ConvertSurface
-    (SDL_Surface * src, SDL_PixelFormat * fmt, Uint32 flags);
+    (SDL_Surface * src, const SDL_PixelFormat * fmt, Uint32 flags);
 extern DECLSPEC SDL_Surface *SDLCALL SDL_ConvertSurfaceFormat
     (SDL_Surface * src, Uint32 pixel_format, Uint32 flags);
 
diff --git a/src/video/SDL_surface.c b/src/video/SDL_surface.c
index 84d3a4dc6..1c4631c40 100644
--- a/src/video/SDL_surface.c
+++ b/src/video/SDL_surface.c
@@ -801,7 +801,7 @@ SDL_UnlockSurface(SDL_Surface * surface)
  * Convert a surface into the specified pixel format.
  */
 SDL_Surface *
-SDL_ConvertSurface(SDL_Surface * surface, SDL_PixelFormat * format,
+SDL_ConvertSurface(SDL_Surface * surface, const SDL_PixelFormat * format,
                    Uint32 flags)
 {
     SDL_Surface *convert;