diff --git a/CHANGELOG b/CHANGELOG
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -2,6 +2,7 @@
 ------------
   * expose more of the cpphs API
   * allow the static linking exception to the LGPL
+  * (1.19.1): don't warn about trailing comments in #ifdefs
 
 Version 1.18
 ------------
diff --git a/Language/Preprocessor/Cpphs/CppIfdef.hs b/Language/Preprocessor/Cpphs/CppIfdef.hs
--- a/Language/Preprocessor/Cpphs/CppIfdef.hs
+++ b/Language/Preprocessor/Cpphs/CppIfdef.hs
@@ -190,11 +190,14 @@
         case runParser parseBoolExp s of
           (Left msg, _) -> error ("Cannot parse #if directive in file "++show p
                                  ++":\n    "++msg)
-          (Right b, xs) -> do when (any (not . isSpace) xs) $
+          (Right b, xs) -> do when (any (not . isSpace) xs && notComment xs) $
                                    hPutStrLn stderr
                                      ("Warning: trailing characters after #if"
                                       ++" directive in file "++show p++": "++xs)
                               return b
+
+notComment = not . ("//"`isPrefixOf`) . dropWhile isSpace
+
 
 -- | The preprocessor must expand all macros (recursively) before evaluating
 --   the conditional.
diff --git a/cpphs.cabal b/cpphs.cabal
--- a/cpphs.cabal
+++ b/cpphs.cabal
@@ -1,5 +1,5 @@
 Name: cpphs
-Version: 1.19
+Version: 1.19.1
 Copyright: 2004-2015, Malcolm Wallace
 License: LGPL
 License-File: LICENCE-LGPL
diff --git a/cpphs.hs b/cpphs.hs
--- a/cpphs.hs
+++ b/cpphs.hs
@@ -20,7 +20,7 @@
 import Data.List   ( isPrefixOf )
 
 version :: String
-version = "1.19"
+version = "1.19.1"
 
 main :: IO ()
 main = do
diff --git a/docs/index.html b/docs/index.html
--- a/docs/index.html
+++ b/docs/index.html
@@ -198,11 +198,11 @@
 <b>Current stable version:</b>
 
 <p>
-cpphs-1.19, release date 2015-03-30<br>
+cpphs-1.19.1, release date 2015-07-30<br>
 By HTTP:
 <a href="http://hackage.haskell.org/package/cpphs">Hackage</a>.
 <ul>
-<li> expose more of the API
+<li> don't warn about trailing comments in #ifdefs
 </ul>
 
 <p>
@@ -224,6 +224,14 @@
 
 <p>
 <b>Older versions:</b>
+
+<p>
+cpphs-1.19, release date 2015-03-30<br>
+By HTTP:
+<a href="http://hackage.haskell.org/package/cpphs">Hackage</a>.
+<ul>
+<li> expose more of the API
+</ul>
 
 <p>
 cpphs-1.18.9, release date 2015-02-19<br>