diff --git a/bl31/bl31.mk b/bl31/bl31.mk
index 878cea5..3e665c5 100644
--- a/bl31/bl31.mk
+++ b/bl31/bl31.mk
@@ -148,7 +148,8 @@
 endif
 
 ifeq (${DRTM_SUPPORT},1)
-BL31_SOURCES		+=	services/std_svc/drtm/drtm_main.c
+BL31_SOURCES		+=	services/std_svc/drtm/drtm_main.c	\
+				${MBEDTLS_SOURCES}
 endif
 
 BL31_LINKERFILE		:=	bl31/bl31.ld.S