diff --git a/util/mkdef.pl b/util/mkdef.pl
index 07117e93a998ba0fb24421b3fa48f12fb53bf4e5..85781711ef676af76f0679d1a78c51e40701f3c9 100755
--- a/util/mkdef.pl
+++ b/util/mkdef.pl
@@ -116,6 +116,8 @@ my @known_algorithms = ( "RC2", "RC4", "RC5", "IDEA", "DES", "BF",
 		 	 "SSL_TRACE",
 			 # Unit testing
 		 	 "UNIT_TEST",
+			 # User Interface
+			 "UI",
 			 # OCB mode
 			 "OCB",
                          # APPLINK (win build feature?)