diff --git a/sys/conf/files b/sys/conf/files
index ce2ac725866d..bb70b43ee6cc 100644
--- a/sys/conf/files
+++ b/sys/conf/files
@@ -1480,7 +1480,8 @@ dev/mps/mps.c			optional mps
 dev/mps/mps_config.c		optional mps
 dev/mps/mps_mapping.c		optional mps
 dev/mps/mps_pci.c		optional mps pci
-dev/mps/mps_sas.c		optional mps
+dev/mps/mps_sas.c		optional mps \
+	compile-with "${NORMAL_C} ${NO_WUNNEEDED_INTERNAL_DECL}"
 dev/mps/mps_sas_lsi.c		optional mps
 dev/mps/mps_table.c		optional mps
 dev/mps/mps_user.c		optional mps
diff --git a/sys/conf/kern.mk b/sys/conf/kern.mk
index 1dfc9fbe674a..5cb718ede462 100644
--- a/sys/conf/kern.mk
+++ b/sys/conf/kern.mk
@@ -23,6 +23,7 @@ NO_WSHIFT_COUNT_OVERFLOW=	-Wno-shift-count-overflow
 NO_WUNUSED_VALUE=		-Wno-unused-value
 NO_WSELF_ASSIGN=		-Wno-self-assign
 NO_WFORMAT_SECURITY=		-Wno-format-security
+NO_WUNNEEDED_INTERNAL_DECL=	-Wno-unneeded-internal-declaration
 # Several other warnings which might be useful in some cases, but not severe
 # enough to error out the whole kernel build.  Display them anyway, so there is
 # some incentive to fix them eventually.
diff --git a/sys/modules/mps/Makefile b/sys/modules/mps/Makefile
index b8589647fef8..d8f82c6a98e3 100644
--- a/sys/modules/mps/Makefile
+++ b/sys/modules/mps/Makefile
@@ -11,3 +11,6 @@ SRCS+=	device_if.h bus_if.h pci_if.h
 #CFLAGS += -DMPS_DEBUG
 
 .include <bsd.kmod.mk>
+
+CWARNFLAGS.mps_sas.c=	${NO_WUNNEEDED_INTERNAL_DECL}
+CWARNFLAGS+=		${CWARNFLAGS.${.IMPSRC:T}}