diff --git a/ChangeLog b/ChangeLog
index 6b447ee1b1..6f91616fd1 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Tue Aug 21 21:59:22 2012  Ayumu AIZAWA  <ayumu.aizawa@gmail.com>
+
+	* lib/observer.rb: fix typo. https://github.com/ruby/ruby/pull/162 by
+	  unsymbol (Philip Cunningham).
+
 Tue Aug 21 20:30:06 2012  Benoit Daloze  <eregontp@gmail.com>
 
 	* test/fileutils/test_fileutils.rb (TestFileUtils#teardown):
diff --git a/lib/observer.rb b/lib/observer.rb
index 688b1f556b..208d8ed6ed 100644
--- a/lib/observer.rb
+++ b/lib/observer.rb
@@ -184,7 +184,7 @@ module Observable
   # Notify observers of a change in state *if* this object's changed state is
   # +true+.
   #
-  # This will invoke the method named in #add_observer, pasing <tt>*arg</tt>.
+  # This will invoke the method named in #add_observer, passing <tt>*arg</tt>.
   # The changed state is then set to +false+.
   #
   # <tt>*arg</tt>:: Any arguments to pass to the observers.