diff --git a/lib/libsm/Makefile b/lib/libsm/Makefile
index f2f19fb4cf4a..ce590d71f058 100644
--- a/lib/libsm/Makefile
+++ b/lib/libsm/Makefile
@@ -18,11 +18,6 @@ CFLAGS+=${SENDMAIL_CFLAGS}
 
 WARNS?=	2
 
-# Unfortunately, clang gives warnings about sendmail code that cannot
-# be turned off yet.  Since this is contrib code, and we don't really
-# care about the warnings, just make them non-fatal for now.
-NO_WERROR.clang=
-
 LIB=	sm
 
 SRCS+=	sm_os.h
diff --git a/libexec/mail.local/Makefile b/libexec/mail.local/Makefile
index 1487decf6216..3e59609e893e 100644
--- a/libexec/mail.local/Makefile
+++ b/libexec/mail.local/Makefile
@@ -12,11 +12,6 @@ CFLAGS+=-I${SENDMAIL_DIR}/include -I.
 WARNS?=	2
 WFORMAT=0
 
-# Unfortunately, clang gives warnings about sendmail code that cannot
-# be turned off yet.  Since this is contrib code, and we don't really
-# care about the warnings, just make them non-fatal for now.
-NO_WERROR.clang=
-
 LIBSMDIR=	${.OBJDIR}/../../lib/libsm
 LIBSM=		${LIBSMDIR}/libsm.a
 
diff --git a/libexec/smrsh/Makefile b/libexec/smrsh/Makefile
index 0de820d02279..ae86155d0d00 100644
--- a/libexec/smrsh/Makefile
+++ b/libexec/smrsh/Makefile
@@ -17,11 +17,6 @@ LDADD=	${LIBSM}
 
 WARNS?=	2
 
-# Unfortunately, clang gives warnings about sendmail code that cannot
-# be turned off yet.  Since this is contrib code, and we don't really
-# care about the warnings, just make them non-fatal for now.
-NO_WERROR.clang=
-
 SRCS+=	sm_os.h
 CLEANFILES+=sm_os.h
 
diff --git a/share/mk/bsd.sys.mk b/share/mk/bsd.sys.mk
index 847e571e0d17..1d8b49d4142a 100644
--- a/share/mk/bsd.sys.mk
+++ b/share/mk/bsd.sys.mk
@@ -72,7 +72,7 @@ CWARNFLAGS+=	-Wno-tautological-compare -Wno-unused-value\
 		-Wno-parentheses-equality -Wno-unused-function -Wno-conversion
 .endif # WARNS <= 3
 .if ${WARNS} <= 2
-CWARNFLAGS+=	-Wno-switch -Wno-switch-enum
+CWARNFLAGS+=	-Wno-switch -Wno-switch-enum -Wno-knr-promoted-parameter
 .endif # WARNS <= 2
 .if ${WARNS} <= 1
 CWARNFLAGS+=	-Wno-parentheses
diff --git a/usr.bin/vacation/Makefile b/usr.bin/vacation/Makefile
index ad77dbae8c71..056f5764fa01 100644
--- a/usr.bin/vacation/Makefile
+++ b/usr.bin/vacation/Makefile
@@ -11,11 +11,6 @@ CFLAGS+=-D_FFR_LISTDB -D_FFR_DEBUG
 
 WARNS?=	2
 
-# Unfortunately, clang gives warnings about sendmail code that cannot
-# be turned off yet.  Since this is contrib code, and we don't really
-# care about the warnings, just make them non-fatal for now.
-NO_WERROR.clang=
-
 LIBSMDIR=	${.OBJDIR}/../../lib/libsm
 LIBSM=		${LIBSMDIR}/libsm.a
 
diff --git a/usr.sbin/sendmail/Makefile b/usr.sbin/sendmail/Makefile
index b68ed0fad71d..a9f7fbbafd69 100644
--- a/usr.sbin/sendmail/Makefile
+++ b/usr.sbin/sendmail/Makefile
@@ -45,11 +45,6 @@ CFLAGS+= -DNETINET6
 
 WARNS?=	1
 
-# Unfortunately, clang gives warnings about sendmail code that cannot
-# be turned off yet.  Since this is contrib code, and we don't really
-# care about the warnings, just make them non-fatal for now.
-NO_WERROR.clang=
-
 DPADD=	${LIBUTIL} ${LIBWRAP}
 LDADD=	-lutil -lwrap