diff --git a/meta-arm/recipes-bsp/trusted-firmware-a/trusted-firmware-a.inc b/meta-arm/recipes-bsp/trusted-firmware-a/trusted-firmware-a.inc
index 6a2c0da9..987b7a66 100644
--- a/meta-arm/recipes-bsp/trusted-firmware-a/trusted-firmware-a.inc
+++ b/meta-arm/recipes-bsp/trusted-firmware-a/trusted-firmware-a.inc
@@ -49,10 +49,10 @@ SRC_URI_MBEDTLS ??= ""
 # This should be set to MBEDTLS LIC FILES checksum
 LIC_FILES_CHKSUM_MBEDTLS ??= ""
 # add MBEDTLS to our sources if activated
-SRC_URI:append = " ${@bb.utils.contains('TFA_MBEDTLS', '1', '${SRC_URI_MBEDTLS}', '', d)}"
+SRC_URI += "${@bb.utils.contains('TFA_MBEDTLS', '1', '${SRC_URI_MBEDTLS}', '', d)}"
 # Update license variables
 LICENSE:append = "${@bb.utils.contains('TFA_MBEDTLS', '1', ' & Apache-2.0', '', d)}"
-LIC_FILES_CHKSUM:append = "${@bb.utils.contains('TFA_MBEDTLS', '1', ' ${LIC_FILES_CHKSUM_MBEDTLS}', '', d)}"
+LIC_FILES_CHKSUM += "${@bb.utils.contains('TFA_MBEDTLS', '1', '${LIC_FILES_CHKSUM_MBEDTLS}', '', d)}"
 # add mbed TLS to version
 SRCREV_FORMAT:append = "${@bb.utils.contains('TFA_MBEDTLS', '1', '_mbedtls', '', d)}"