diff --git a/NEWS b/NEWS
index e8fdfe0cf5..aadb1224c9 100644
--- a/NEWS
+++ b/NEWS
@@ -194,8 +194,8 @@ Fiber::
 File::
   Modified method::
 
-    * File.extname now returns a dot string at a name ending with a
-      dot.  [Bug #15267]
+    * File.extname now returns a dot string at a name ending with a dot on
+      non-Windows platforms.  [Bug #15267]
 
           File.extname("foo.") #=> "."
 
diff --git a/file.c b/file.c
index d10aeaa3e0..17881c065d 100644
--- a/file.c
+++ b/file.c
@@ -4789,10 +4789,13 @@ ruby_enc_find_extname(const char *name, long *len, rb_encoding *enc)
  *  An empty string will also be returned when the period is the last character
  *  in +path+.
  *
+ *  On Windows, trailing dots are truncated.
+ *
  *     File.extname("test.rb")         #=> ".rb"
  *     File.extname("a/b/d/test.rb")   #=> ".rb"
  *     File.extname(".a/b/d/test.rb")  #=> ".rb"
- *     File.extname("foo.")            #=> "."
+ *     File.extname("foo.")            #=> "" on Windows
+ *     File.extname("foo.")            #=> "." on non-Windows
  *     File.extname("test")            #=> ""
  *     File.extname(".profile")        #=> ""
  *     File.extname(".profile.sh")     #=> ".sh"