diff --git a/ChangeLog b/ChangeLog
index 6020f8d35e..b95e24657e 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Wed Jun 13 17:50:43 2012  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* Makefile.in (.c.i): add warnflags to make the result consistent with
+	  compilation.
+
 Wed Jun 13 15:12:07 2012  URABE Shyouhei  <shyouhei@ruby-lang.org>
 
 	* configure.in: On Windows  platforms, system provided headers are
diff --git a/Makefile.in b/Makefile.in
index 2fe2d1c0e6..1c5bdb7961 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -315,7 +315,7 @@ enc/unicode/name2ctype.h: enc/unicode/name2ctype.kwd
 
 .c.i:
 	@$(ECHO) preprocessing $<
-	$(Q) $(CPP) $(XCFLAGS) $(CPPFLAGS) $(COUTFLAG)$@ -E $< > $@
+	$(Q) $(CPP) $(warnflags) $(XCFLAGS) $(CPPFLAGS) $(COUTFLAG)$@ -E $< > $@
 
 clean-local::
 	$(Q)$(RM) ext/extinit.c ext/extinit.$(OBJEXT) ext/ripper/y.output \