diff --git a/lib/irb/color.rb b/lib/irb/color.rb
index fa99ed6fd..42de0155e 100644
--- a/lib/irb/color.rb
+++ b/lib/irb/color.rb
@@ -15,6 +15,7 @@ module Color
     BLUE      = 34
     MAGENTA   = 35
     CYAN      = 36
+    WHITE     = 37
 
     TOKEN_KEYWORDS = {
       on_kw: ['nil', 'self', 'true', 'false', '__FILE__', '__LINE__', '__ENCODING__'],