diff --git a/drivers/auth/mbedtls/mbedtls_common.mk b/drivers/auth/mbedtls/mbedtls_common.mk
index 0a4775d..3eb4161 100644
--- a/drivers/auth/mbedtls/mbedtls_common.mk
+++ b/drivers/auth/mbedtls/mbedtls_common.mk
@@ -48,6 +48,7 @@
 					rsa_internal.c				\
 					x509.c 					\
 					x509_crt.c 				\
+					constant_time.c 			\
 					)
 
 # The platform may define the variable 'TF_MBEDTLS_KEY_ALG' to select the key