--- man/Makefile.am.orig	2015-04-15 14:14:46.957617700 +0300
+++ man/Makefile.am	2015-04-15 14:15:38.508110948 +0300
@@ -9,7 +9,7 @@
 
 AM_CPPFLAGS = -I$(top_builddir) -I$(top_srcdir)
 filenames.sed: filenames.sed.c
-	$(AM_V_GEN)$(CPP) $(DEFS) $(DEFAULT_INCLUDES) $(INCLUDES) \
+	$(AM_V_GEN)$(CPP) -P $(DEFS) $(DEFAULT_INCLUDES) $(INCLUDES) \
 	    $(AM_CPPFLAGS) $(CPPFLAGS) $(srcdir)/filenames.sed.c | \
 	    $(SED) -n -e '/s|__/ p' -e '/^\/__/ p' > $@