diff --git a/board/stmicroelectronics/common/stm32mp157/post-image.sh b/board/stmicroelectronics/common/stm32mp157/post-image.sh
index 65809e46a4..0cf52f4564 100755
--- a/board/stmicroelectronics/common/stm32mp157/post-image.sh
+++ b/board/stmicroelectronics/common/stm32mp157/post-image.sh
@@ -8,7 +8,7 @@
 #
 atf_image()
 {
-	ATF_VARIABLES="$(sed -n 's/^BR2_TARGET_ARM_TRUSTED_FIRMWARE_ADDITIONAL_VARIABLES="\([\/a-zA-Z0-9_=. \-]*\)"$/\1/p' ${BR2_CONFIG})"
+	ATF_VARIABLES="$(sed -n 's/^BR2_TARGET_ARM_TRUSTED_FIRMWARE_ADDITIONAL_VARIABLES="\([^\"]*\)"$/\1/p' ${BR2_CONFIG})"
 	# make sure DTB_FILE_NAME is set
 	printf '%s\n' "${ATF_VARIABLES}" | grep -Eq 'DTB_FILE_NAME=[0-9A-Za-z_\-]*'
 	# extract the value