diff --git a/sys/conf/kern.mk b/sys/conf/kern.mk
index 55f7d998bc1a..5676057d3d4b 100644
--- a/sys/conf/kern.mk
+++ b/sys/conf/kern.mk
@@ -30,8 +30,10 @@ CWARNFLAGS?=	-Wall -Wredundant-decls -Wnested-externs -Wstrict-prototypes \
 # reserved for user applications.
 #
 .if ${MACHINE_ARCH} == "i386" && ${CC} != "icc"
-CFLAGS+=	-mno-align-long-strings -mpreferred-stack-boundary=2 \
-		-mno-mmx -mno-3dnow -mno-sse -mno-sse2 -mno-sse3
+.if ${CC} != "clang"
+CFLAGS+=	-mno-align-long-strings -mpreferred-stack-boundary=2
+.endif
+CFLAGS+=	-mno-mmx -mno-3dnow -mno-sse -mno-sse2 -mno-sse3
 INLINE_LIMIT?=	8000
 .endif
 
diff --git a/sys/conf/kern.pre.mk b/sys/conf/kern.pre.mk
index b4747f71c9ac..5c22abd48ddd 100644
--- a/sys/conf/kern.pre.mk
+++ b/sys/conf/kern.pre.mk
@@ -92,7 +92,7 @@ INCLUDES+= -I$S/dev/cxgb
 
 CFLAGS=	${COPTFLAGS} ${C_DIALECT} ${DEBUG} ${CWARNFLAGS}
 CFLAGS+= ${INCLUDES} -D_KERNEL -DHAVE_KERNEL_OPTION_HEADERS -include opt_global.h
-.if ${CC} != "icc"
+.if ${CC} != "icc" && ${CC} != "clang"
 CFLAGS+= -fno-common -finline-limit=${INLINE_LIMIT}
 .if ${MACHINE_CPUARCH} != "mips"
 CFLAGS+= --param inline-unit-growth=100
@@ -109,8 +109,8 @@ WERROR?= -Werror
 ASM_CFLAGS= -x assembler-with-cpp -DLOCORE ${CFLAGS}
 
 .if defined(PROFLEVEL) && ${PROFLEVEL} >= 1
-.if ${CC} == "icc"
-.error "Profiling doesn't work with icc yet"
+.if ${CC} == "icc" || ${CC} == "clang"
+.error "Profiling doesn't work with icc or clang yet"
 .endif
 CFLAGS+=	-DGPROF -falign-functions=16
 .if ${PROFLEVEL} >= 2
diff --git a/sys/conf/kmod.mk b/sys/conf/kmod.mk
index b817b1ba6592..764252061713 100644
--- a/sys/conf/kmod.mk
+++ b/sys/conf/kmod.mk
@@ -114,7 +114,7 @@ CFLAGS+=	-I. -I@
 # for example.
 CFLAGS+=	-I@/contrib/altq
 
-.if ${CC} != "icc"
+.if ${CC} != "icc" && ${CC} != "clang"
 CFLAGS+=	-finline-limit=${INLINE_LIMIT}
 CFLAGS+= --param inline-unit-growth=100
 CFLAGS+= --param large-function-growth=1000