diff -up openssl-1.1.0-pre6/engines/e_chil.c.chil openssl-1.1.0-pre6/engines/e_chil.c
--- openssl-1.1.0-pre6/engines/e_chil.c.chil	2016-08-04 16:00:47.000000000 +0200
+++ openssl-1.1.0-pre6/engines/e_chil.c	2016-08-05 16:50:13.860588775 +0200
@@ -1195,6 +1195,11 @@ static int hwcrhk_insert_card(const char
     UI *ui;
     void *callback_data = NULL;
     UI_METHOD *ui_method = NULL;
+    /* Despite what the documentation says prompt_info can be
+     * an empty string.
+     */
+    if (prompt_info && !*prompt_info)
+        prompt_info = NULL;
 
     if (cactx) {
         if (cactx->ui_method)