diff --git a/testsuite/Makefile.am b/testsuite/Makefile.am
index 9a1d7d95098f63f4955657a5c22358f2d3cb38fb..25304fd87b98ec17cf38c248b8609987d98a287c 100644
--- a/testsuite/Makefile.am
+++ b/testsuite/Makefile.am
@@ -19,8 +19,8 @@ LDADD = testutils.o ../libnettle.a
 EXTRA_DIST = $(M4_FILES) macros.m4 testutils.c testutils.h \
 	     run-tests rfc1750.txt
 
-M4FLAGS = -P -s
-# M4FLAGS = -P
+# M4FLAGS = -P -s
+M4FLAGS = -P
 $(M4_FILES:.m4=.c): %.c: macros.m4 %.m4
 	$(M4) $(M4FLAGS) $^ > $@T
 	test -s $@T && mv -f $@T $@