diff --git a/ChangeLog b/ChangeLog
index 1ec72651bb..1a32ddcd31 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -130,6 +130,11 @@ Sun Jun 18 00:49:11 2006  Tanaka Akira  <akr@m17n.org>
 	  (unix_recvfrom_nonblock): removed.
 	  UNIXSocket#recvfrom_nonblock is removed.
 
+Sat Jun 17 22:17:17 2006  Yukihiro Matsumoto  <matz@ruby-lang.org>
+
+	* lib/mathn.rb (Integer::prime_division): raise ZeroDivisionError
+	  on zeros.  [ruby-dev:28739]
+
 Sat Jun 17 14:53:32 2006  Tanaka Akira  <akr@m17n.org>
 
 	* lib/pathname.rb: backport from 1.9.
diff --git a/lib/drb/drb.rb b/lib/drb/drb.rb
index 2177af871b..dac7a9b02c 100644
--- a/lib/drb/drb.rb
+++ b/lib/drb/drb.rb
@@ -430,12 +430,15 @@ module DRb
     end
   end
 
+  # An exception wrapping an error object
   class DRbRemoteError < DRbError
     def initialize(error)
       @reason = error.class.to_s
       super("#{error.message} (#{error.class})")
       set_backtrace(error.backtrace)
     end
+
+    # the class of the error, as a string.
     attr_reader :reason
   end
 
diff --git a/lib/mathn.rb b/lib/mathn.rb
index 14e2e9272c..a5a121c6c6 100644
--- a/lib/mathn.rb
+++ b/lib/mathn.rb
@@ -43,6 +43,7 @@ class Integer
   end
   
   def prime_division
+    raise ZeroDivisionError if self == 0
     ps = Prime.new
     value = self
     pv = []