diff --git a/koans/edgecase.rb b/koans/edgecase.rb
index 0707687..1443807 100644
--- a/koans/edgecase.rb
+++ b/koans/edgecase.rb
@@ -24,6 +24,11 @@ def in_ruby_version(*versions)
   yield if versions.any? { |v| ruby_version?(v) }
 end
 
+in_ruby_version("1.8") do
+  class KeyError < StandardError
+  end
+end
+
 # Standard, generic replacement value.
 # If value19 is given, it is used in place of value for Ruby 1.9.
 def __(value="FILL ME IN", value19=:mu)
@@ -44,8 +49,12 @@ def _n_(value=999999, value19=:mu)
 end
 
 # Error object replacement value.
-def ___(value=FillMeInError)
-  value
+def ___(value=FillMeInError, value19=:mu)
+  if RUBY_VERSION < "1.9"
+    value
+  else
+    (value19 == :mu) ? value : value19
+  end
 end
 
 # Method name replacement.