diff --git a/ChangeLog b/ChangeLog
index c92bfb8d54..d65df98a97 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Tue Apr 20 00:43:03 2010  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* file.c (rb_file_s_extname): skip last directory separators.
+	  [ruby-core:29627]
+
 Tue Apr 20 00:41:25 2010  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* io.c (internal_{read,write}_func, rb_{read,write}_internal):
diff --git a/file.c b/file.c
index af2730a12f..f9f8192637 100644
--- a/file.c
+++ b/file.c
@@ -3500,7 +3500,7 @@ rb_file_s_extname(VALUE klass, VALUE fname)
     if (!p)
 	p = name;
     else
-	name = ++p;
+	do name = ++p; while (isdirsep(*p));
 
     e = 0;
     while (*p && *p == '.') p++;
diff --git a/test/ruby/test_file_exhaustive.rb b/test/ruby/test_file_exhaustive.rb
index 4a26e435b8..634197e0a7 100644
--- a/test/ruby/test_file_exhaustive.rb
+++ b/test/ruby/test_file_exhaustive.rb
@@ -454,6 +454,8 @@ class TestFileExhaustive < Test::Unit::TestCase
         end
       end
     end
+    bug3175 = '[ruby-core:29627]'
+    assert_equal(".rb", File.extname("/tmp//bla.rb"), bug3175)
 
     assert_incompatible_encoding {|d| File.extname(d)}
   end