diff --git a/lib/weakref.rb b/lib/weakref.rb
index d4ffa65395..c88babba46 100644
--- a/lib/weakref.rb
+++ b/lib/weakref.rb
@@ -78,7 +78,7 @@ class WeakRef < Delegator
   # Creates a weak reference to +orig+
   #
   # Raises an ArgumentError if the given +orig+ is immutable, such as Symbol,
-  # Fixnum, or Float.
+  # Integer, or Float.
 
   def initialize(orig)
     case orig