--- a/libvips/foreign/foreign.c
+++ b/libvips/foreign/foreign.c
@@ -1529,6 +1529,8 @@ vips__foreign_convert_saveable(VipsImage *in, VipsImage **ready,
 	VipsForeignSaveable saveable, VipsBandFormat *format, VipsCoding *coding,
 	VipsArrayDouble *background)
 {
+	VipsBandFormat original_format = in->BandFmt;
+
 	VipsImage *out;
 
 	/* in holds a reference to the output of our chain as we build it.
@@ -1642,7 +1644,7 @@ vips__foreign_convert_saveable(VipsImage *in, VipsImage **ready,
 	/* Convert to the format the saver likes.
 	 */
 	if (in->Coding == VIPS_CODING_NONE) {
-		if (vips_cast(in, &out, format[in->BandFmt], NULL)) {
+		if (vips_cast(in, &out, format[original_format], NULL)) {
 			g_object_unref(in);
 			return -1;
 		}