diff --git a/bl31/bl31.mk b/bl31/bl31.mk
index ccd54bb..7819141 100644
--- a/bl31/bl31.mk
+++ b/bl31/bl31.mk
@@ -98,6 +98,10 @@
 BL31_SOURCES		+=      lib/extensions/sys_reg_trace/aarch64/sys_reg_trace.c
 endif
 
+ifeq (${ENABLE_TRF_FOR_NS},1)
+BL31_SOURCES		+=	lib/extensions/trf/aarch64/trf.c
+endif
+
 ifeq (${WORKAROUND_CVE_2017_5715},1)
 BL31_SOURCES		+=	lib/cpus/aarch64/wa_cve_2017_5715_bpiall.S	\
 				lib/cpus/aarch64/wa_cve_2017_5715_mmu.S