diff --git a/mail-filter/libmilter/libmilter-1.0.2_p3-r2.ebuild b/mail-filter/libmilter/libmilter-1.0.2_p3-r2.ebuild
index 2b6d8f6de2772..c2431df63e884 100644
--- a/mail-filter/libmilter/libmilter-1.0.2_p3-r2.ebuild
+++ b/mail-filter/libmilter/libmilter-1.0.2_p3-r2.ebuild
@@ -39,6 +39,7 @@ KEYWORDS="~alpha amd64 arm arm64 ~hppa ~ia64 ~ppc ppc64 ~riscv ~s390 sparc x86"
 IUSE="ipv6 poll"
 
 RDEPEND="!<mail-mta/sendmail-8.16.1"
+BDEPEND="sys-devel/m4"
 
 # build system patch copied from sendmail ebuild
 PATCHES=(