diff --git a/ChangeLog b/ChangeLog
index 88866e64ca..35c8464d99 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+Mon Sep 15 22:34:39 2014  Natalie Weizenbaum  <nweiz@google.com>
+
+	* ext/pathname/lib/pathname.rb (SAME_PATHS):
+	  Pathname#relative_path_from uses String#casecmp to compare strings
+	  on case-insensitive filesystem platforms (e.g., Windows). This can
+	  return nil for strings with different encodings, and the code
+	  previously assumed that it always returned a Fixnum.  [Fix GH-713]
+
 Mon Sep 15 22:31:33 2014  Sho Hashimoto  <sho.hsmt@gmail.com>
 
 	* ext/fiddle/lib/fiddle/import.rb (Fiddle::Importer#sizeof): fix typo,
diff --git a/ext/pathname/lib/pathname.rb b/ext/pathname/lib/pathname.rb
index e7e47ceac6..8bce81ea10 100644
--- a/ext/pathname/lib/pathname.rb
+++ b/ext/pathname/lib/pathname.rb
@@ -22,7 +22,8 @@ class Pathname
   end
 
   SAME_PATHS = if File::FNM_SYSCASE.nonzero?
-    proc {|a, b| a.casecmp(b).zero?}
+    # Avoid #zero? here because #casecmp can return nil.
+    proc {|a, b| a.casecmp(b) == 0}
   else
     proc {|a, b| a == b}
   end
diff --git a/test/pathname/test_pathname.rb b/test/pathname/test_pathname.rb
index c61e613d9b..557fae35bc 100644
--- a/test/pathname/test_pathname.rb
+++ b/test/pathname/test_pathname.rb
@@ -1322,4 +1322,17 @@ class TestPathname < Test::Unit::TestCase
       assert_equal("foo/bar", File.join(Pathname.new("foo"), Pathname.new("bar").taint))
     }.call
   end
+
+  def test_relative_path_from_casefold
+    assert_separately([], <<-'end;') #    do
+      module File::Constants
+        remove_const :FNM_SYSCASE
+        FNM_SYSCASE = FNM_CASEFOLD
+      end
+      require 'pathname'
+      foo = Pathname.new("fo\u{f6}")
+      bar = Pathname.new("b\u{e4}r".encode("ISO-8859-1"))
+      assert_instance_of(Pathname, foo.relative_path_from(bar))
+    end;
+  end
 end
diff --git a/version.h b/version.h
index 4cf2979696..9c7b05d8a0 100644
--- a/version.h
+++ b/version.h
@@ -1,6 +1,6 @@
 #define RUBY_VERSION "2.1.2"
 #define RUBY_RELEASE_DATE "2014-09-15"
-#define RUBY_PATCHLEVEL 239
+#define RUBY_PATCHLEVEL 240
 
 #define RUBY_RELEASE_YEAR 2014
 #define RUBY_RELEASE_MONTH 9