diff --git a/include/vips/format.h b/include/vips/format.h
index a376d0b3..4d72038e 100644
--- a/include/vips/format.h
+++ b/include/vips/format.h
@@ -110,7 +110,8 @@ void *vips_format_map( VSListMap2Fn fn, void *a, void *b );
 VipsFormatClass *vips_format_for_file( const char *filename );
 VipsFormatClass *vips_format_for_name( const char *filename );
 
-VipsFormatFlags vips_format_get_flags( VipsFormatClass *format );
+VipsFormatFlags vips_format_get_flags( VipsFormatClass *format, 
+	const char *filename );
 
 /* Read/write an image convenience functions.
  */
diff --git a/libsrc/format/format.c b/libsrc/format/format.c
index af85b5bb..0aba31f0 100644
--- a/libsrc/format/format.c
+++ b/libsrc/format/format.c
@@ -126,7 +126,7 @@ vips_format_init( VipsFormat *object )
 }
 
 VipsFormatFlags
-vips_format_get_flags( VipsFormatClass *format )
+vips_format_get_flags( VipsFormatClass *format, const char *filename )
 {
 	return( format->get_flags ? format->get_flags( filename ) : 0 );
 }