diff --git a/src/ikarus.boot b/src/ikarus.boot
index 3bbddd6..06f725e 100644
Binary files a/src/ikarus.boot and b/src/ikarus.boot differ
diff --git a/src/makefile.ss b/src/makefile.ss
index 45406e6..1f4f832 100755
--- a/src/makefile.ss
+++ b/src/makefile.ss
@@ -119,6 +119,7 @@
     [syncase     (r6rs syntax-case)           #t]
     [rfl         (r6rs arithmetic flonums)    #t]
     [mutable-pairs (r6rs mutable-pairs)       #t]
+    [unicode     (r6rs unicode)               #t]
     [cm          (chez modules)               #t]
     [$all        (ikarus system $all)         #f]
     [$pairs      (ikarus system $pairs)       #f]
@@ -151,6 +152,7 @@
     [r           (r6rs)                       #t]
     [syncase     (r6rs syntax-case)           #t]
     [mutable-pairs (r6rs mutable-pairs)       #t]
+    [unicode     (r6rs unicode)               #t]
     [rfl         (r6rs arithmetic flonums)    #t]
     [cm          (chez modules)               #t]
     [$all        (ikarus system $all)         #f]
@@ -299,10 +301,10 @@
     [integer->char           i r]
     [char->integer           i r]
     [char-whitespace?        i r]
-    [char-downcase           i]
-    [char-upcase             i]
-    [char-titlecase          i]
-    [char-foldcase           i]
+    [char-downcase           i unicode]
+    [char-upcase             i unicode]
+    [char-titlecase          i unicode]
+    [char-foldcase           i unicode]
     [string?                 i r]
     [string                  i r]
     [make-string             i r]