diff --git a/src/aclocal.m4 b/src/aclocal.m4
index 53aac95064b6f3b6d5312ae3ef490ca93c04a253..a5a919bfb05949180edaab1b563cecd3af9f8c66 100644
--- a/src/aclocal.m4
+++ b/src/aclocal.m4
@@ -502,7 +502,8 @@ EOF
 ])
 
 m4_copy([AC_CHECK_HEADERS], [ORIG_CHECK_HEADERS])
-ifdef([_AC_CHECK_HEADERS], m4_copy([_AC_CHECK_HEADERS], [_ORIG_CHECK_HEADERS]))
+ifdef([_AC_CHECK_HEADERS],
+	[m4_copy([_AC_CHECK_HEADERS], [_ORIG_CHECK_HEADERS])])
 define([AC_CHECK_HEADERS],
 [
   if test "x$enable_binary" != "xno"; then