diff --git a/service/mk/ptos.mk b/service/mk/ptos.mk
index 76dfc52..1f0843d 100644
--- a/service/mk/ptos.mk
+++ b/service/mk/ptos.mk
@@ -32,7 +32,7 @@ SYS_CFLAGS =			\
 	-fno-stack-protector\
 	-D_ST_MULTICORE     \
 
-ifeq ($(ST_TARGET_ARCH),amd64)
+ifeq ($(PT_TARGET_ARCH),amd64)
 	SYS_CFLAGS += 		\
 		-mno-sse		\
 		-mno-sse2		\