diff --git a/libvips/foreign/jxl2vips.c b/libvips/foreign/jxl2vips.c
index cfbba105..5392e492 100644
--- a/libvips/foreign/jxl2vips.c
+++ b/libvips/foreign/jxl2vips.c
@@ -212,6 +212,11 @@ vips_foreign_load_jxl_fill_input( VipsForeignLoadJxl *jxl,
 		return( -1 );
 	jxl->bytes_in_buffer = bytes_read + bytes_remaining;
 
+#ifdef DEBUG_VERBOSE
+	printf( "vips_foreign_load_jxl_fill_input: %zd bytes read\n", 
+		bytes_read );
+#endif /*DEBUG_VERBOSE*/
+
 	return( 0 );
 }