diff --git a/libcpp/ChangeLog b/libcpp/ChangeLog
index fefb2f02ab5..5c4b7a09f09 100644
--- a/libcpp/ChangeLog
+++ b/libcpp/ChangeLog
@@ -1,3 +1,7 @@
+2017-03-16  Jason Merrill  <jason@redhat.com>
+
+	* init.c (cpp_init_builtins): Update __cplusplus for C++17.
+
 2017-02-09  Gerald Pfeifer  <gerald@pfeifer.com>
 
 	* Makefile.in (po/$(PACKAGE).pot): Adjust bug reporting URL.
diff --git a/libcpp/init.c b/libcpp/init.c
index 0679b7f9e36..1477673245a 100644
--- a/libcpp/init.c
+++ b/libcpp/init.c
@@ -499,7 +499,7 @@ cpp_init_builtins (cpp_reader *pfile, int hosted)
     {
       if (CPP_OPTION (pfile, lang) == CLK_CXX1Z
 	  || CPP_OPTION (pfile, lang) == CLK_GNUCXX1Z)
-	_cpp_define_builtin (pfile, "__cplusplus 201500L");
+	_cpp_define_builtin (pfile, "__cplusplus 201703L");
       else if (CPP_OPTION (pfile, lang) == CLK_CXX14
 	  || CPP_OPTION (pfile, lang) == CLK_GNUCXX14)
 	_cpp_define_builtin (pfile, "__cplusplus 201402L");