diff -up openssl-1.0.2i/engines/e_chil.c.chil openssl-1.0.2i/engines/e_chil.c
--- openssl-1.0.2i/engines/e_chil.c.chil	2016-09-22 12:23:06.000000000 +0200
+++ openssl-1.0.2i/engines/e_chil.c	2016-09-22 13:49:32.532017102 +0200
@@ -1274,6 +1274,11 @@ 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)