diff --git a/util.c b/util.c
index f6997f0..6cb4a79 100644
--- a/util.c
+++ b/util.c
@@ -290,7 +290,7 @@ check_user_challenge_file(const char *chalresp_path, const struct passwd *user,
    *
    * Returns one of AUTH_FOUND, AUTH_NOT_FOUND, AUTH_ERROR
    */
-  int len;
+  size_t len;
   int r;
   int ret = AUTH_NOT_FOUND;
   char *userfile = NULL;
@@ -304,8 +304,10 @@ check_user_challenge_file(const char *chalresp_path, const struct passwd *user,
     filename = user->pw_name;
   }
 
+  /* check for userfile challenge files */
   r = get_user_cfgfile_path(chalresp_path, filename, user, &userfile);
   if (!r) {
+    D (debug_file, "Failed to get user cfgfile path");
     ret = AUTH_ERROR;
     goto out;
   }
@@ -315,8 +317,11 @@ check_user_challenge_file(const char *chalresp_path, const struct passwd *user,
     goto out;
   }
 
+  /* check for userfile-* challenge files */
   len = strlen(userfile) + 2 + 1;
   if ((userfile_pattern = malloc(len)) == NULL) {
+    D (debug_file, "Failed to allocate memory for userfile pattern: %s", strerror(errno));
+    ret = AUTH_ERROR;
     goto out;
   }
   snprintf(userfile_pattern, len, "%s-*", userfile);
@@ -324,12 +329,14 @@ check_user_challenge_file(const char *chalresp_path, const struct passwd *user,
   r = glob(userfile_pattern, 0, NULL, &userfile_glob);
   globfree(&userfile_glob);
   switch (r) {
+    case GLOB_NOMATCH:
+      /* No matches found, so continue */
+      break;
     case 0:
       ret = AUTH_FOUND;
       goto out;
-    case GLOB_NOMATCH:
-      break;
     default:
+      D (debug_file, "Error while checking for %s challenge files: %s", userfile_pattern, strerror(errno));
       ret = AUTH_ERROR;
       goto out;
   }