--- a/swscale_internal.h
+++ b/swscale_internal.h
@@ -294,7 +294,7 @@
                             const int16_t *chrFilter, int16_t **chrSrc, int chrFilterSize,
                             uint8_t *dest, int dstW, int dstY);
 
-const char *sws_format_name(int format);
+const char *sws_format_name(enum PixelFormat format);
 
 //FIXME replace this with something faster
 #define is16BPS(x)      (           \