diff --git a/meta-digi-arm/recipes-bsp/u-boot/u-boot-dey-2015.04/ccimx6/install_linux_fw_sd.txt b/meta-digi-arm/recipes-bsp/u-boot/u-boot-dey-2015.04/ccimx6/install_linux_fw_sd.txt
index beb7f46b5..9b5eeffa9 100644
--- a/meta-digi-arm/recipes-bsp/u-boot/u-boot-dey-2015.04/ccimx6/install_linux_fw_sd.txt
+++ b/meta-digi-arm/recipes-bsp/u-boot/u-boot-dey-2015.04/ccimx6/install_linux_fw_sd.txt
@@ -19,59 +19,58 @@ if test $? -eq 1; then
 	exit;
 fi
 
-# Ask for user confirmation (to be enabled in the future when shipped U-Boot
-# supports the 'askenv' command)
-#askenv install_yn "Do you want to continue? (y/n):" 1
-#if test "${install_yn}" != "y" && test "${install_yn}" != "Y"; then
-#	echo "Aborted.";
-#	exit;
-#fi
-
 # Determine U-Boot file to program basing on module variant
-if test "${module_variant}" = "0x12"; then
-	setenv INSTALL_UBOOT_FILENAME u-boot-ccimx6qsbc2GB.imx;
-elif test "${module_variant}" = "0x02" || test "${module_variant}" = "0x04" || test "${module_variant}" = "0x05" || test "${module_variant}" = "0x11"; then
-	setenv INSTALL_UBOOT_FILENAME u-boot-ccimx6qsbc.imx;
-elif test "${module_variant}" = "0x03" || test "${module_variant}" = "0x0e" || test "${module_variant}" = "0x0f"; then
-	setenv INSTALL_UBOOT_FILENAME u-boot-ccimx6qsbc512MB.imx;
-elif test "${module_variant}" = "0x0b"; then
-	setenv INSTALL_UBOOT_FILENAME u-boot-ccimx6dlsbc.imx;
-elif test "${module_variant}" = "0x0c" || test "${module_variant}" = "0x13"; then
-	setenv INSTALL_UBOOT_FILENAME u-boot-ccimx6dlsbc512MB.imx;
-else
-	if test -z "${INSTALL_UBOOT_FILENAME}"; then
-		echo "[ERROR] Cannot determine U-Boot file for this module!";
-		echo "";
-		echo "1. Set variable 'INSTALL_UBOOT_FILENAME' depending on your ConnectCore 6 variant:";
-		echo "   - For a Quad/Dual CPU with 2GB DDR3, run:";
-		echo "     => setenv INSTALL_UBOOT_FILENAME u-boot-ccimx6qsbc2GB.imx";
-		echo "   - For a Quad/Dual CPU with 1GB DDR3, run:";
-		echo "     => setenv INSTALL_UBOOT_FILENAME u-boot-ccimx6qsbc.imx";
-		echo "   - For a Quad/Dual CPU with 512MB DDR3, run:";
-		echo "     => setenv INSTALL_UBOOT_FILENAME u-boot-ccimx6qsbc512MB.imx";
-		echo "   - For a DualLite/Solo CPU with 1GB DDR3, run:";
-		echo "     => setenv INSTALL_UBOOT_FILENAME u-boot-ccimx6dlsbc.imx";
-		echo "   - For a DualLite/Solo CPU with 512MB DDR3, run:";
-		echo "     => setenv INSTALL_UBOOT_FILENAME u-boot-ccimx6dlsbc512MB.imx";
-		echo "";
-		echo "2. Run the install script again.";
-		echo "";
-		echo "Aborted";
-		exit;
-	fi;
+if test -n "${module_variant}"; then
+	if test "${module_variant}" = "0x12"; then
+		setenv INSTALL_UBOOT_FILENAME u-boot-ccimx6qsbc2GB.imx;
+	elif test "${module_variant}" = "0x02" || test "${module_variant}" = "0x04" || test "${module_variant}" = "0x05" || test "${module_variant}" = "0x11"; then
+		setenv INSTALL_UBOOT_FILENAME u-boot-ccimx6qsbc.imx;
+	elif test "${module_variant}" = "0x03" || test "${module_variant}" = "0x0e" || test "${module_variant}" = "0x0f"; then
+		setenv INSTALL_UBOOT_FILENAME u-boot-ccimx6qsbc512MB.imx;
+	elif test "${module_variant}" = "0x0b"; then
+		setenv INSTALL_UBOOT_FILENAME u-boot-ccimx6dlsbc.imx;
+	elif test "${module_variant}" = "0x0c" || test "${module_variant}" = "0x13"; then
+		setenv INSTALL_UBOOT_FILENAME u-boot-ccimx6dlsbc512MB.imx;
+	fi
 fi
+# Use 'test -n ...' because 'test -z ...' does not work well on old versions of
+# u-boot when the checked value is empty.
+if test -n "${INSTALL_UBOOT_FILENAME}"; then
+	true;
+else
+	echo "";
+	echo "[ERROR] Cannot determine U-Boot file for this module!";
+	echo "";
+	echo "1. Set variable 'INSTALL_UBOOT_FILENAME' depending on your ConnectCore 6 variant:";
+	echo "   - For a Quad/Dual CPU with 2GB DDR3, run:";
+	echo "     => setenv INSTALL_UBOOT_FILENAME u-boot-ccimx6qsbc2GB.imx";
+	echo "   - For a Quad/Dual CPU with 1GB DDR3, run:";
+	echo "     => setenv INSTALL_UBOOT_FILENAME u-boot-ccimx6qsbc.imx";
+	echo "   - For a Quad/Dual CPU with 512MB DDR3, run:";
+	echo "     => setenv INSTALL_UBOOT_FILENAME u-boot-ccimx6qsbc512MB.imx";
+	echo "   - For a DualLite/Solo CPU with 1GB DDR3, run:";
+	echo "     => setenv INSTALL_UBOOT_FILENAME u-boot-ccimx6dlsbc.imx";
+	echo "   - For a DualLite/Solo CPU with 512MB DDR3, run:";
+	echo "     => setenv INSTALL_UBOOT_FILENAME u-boot-ccimx6dlsbc512MB.imx";
+	echo "";
+	echo "2. Run the install script again.";
+	echo "";
+	echo "Aborted";
+	echo "";
+	exit;
+fi;
 
 setenv INSTALL_LINUX_FILENAME dey-image-qt-##GRAPHICAL_BACKEND##-ccimx6sbc.boot.vfat
 setenv INSTALL_ROOTFS_FILENAME dey-image-qt-##GRAPHICAL_BACKEND##-ccimx6sbc.ext4
 
 # Check for presence of firmware files on the SD card
-for install_f in $INSTALL_UBOOT_FILENAME $INSTALL_LINUX_FILENAME $INSTALL_ROOTFS_FILENAME; do
-	if test ! -e mmc 1:1 $install_f; then
-		echo "ERROR: Could not find file $install_f";
+for install_f in ${INSTALL_UBOOT_FILENAME} ${INSTALL_LINUX_FILENAME} ${INSTALL_ROOTFS_FILENAME}; do
+	if test ! -e mmc 1:1 ${install_f}; then
+		echo "ERROR: Could not find file ${install_f}";
 		install_abort=1
 	fi;
 done
-if test "${install_abort}" = "1"; then
+if test -n "${install_abort}"; then
 	echo "Aborted.";
 	exit;
 fi
@@ -92,7 +91,7 @@ echo ""
 echo ">> Installing U-Boot boot loader (target will reset)";
 echo ""
 echo ""
-update uboot mmc 1 fat $INSTALL_UBOOT_FILENAME
+update uboot mmc 1 fat ${INSTALL_UBOOT_FILENAME}
 if test $? -eq 1; then
 	echo "[ERROR] Failed to update U-Boot boot loader!";
 	echo "";
@@ -130,7 +129,7 @@ setenv bootcmd '
 	echo ">> Installing Linux kernel and device tree files";
 	echo "";
 	echo "";
-	update linux mmc 1 fat $INSTALL_LINUX_FILENAME;
+	update linux mmc 1 fat ${INSTALL_LINUX_FILENAME};
 	if test $? -eq 1; then
 		echo "[ERROR] Failed to update linux partition!";
 		echo "";
@@ -142,7 +141,7 @@ setenv bootcmd '
 	echo ">> Installing Linux root file system";
 	echo "";
 	echo "";
-	update rootfs mmc 1 fat $INSTALL_ROOTFS_FILENAME;
+	update rootfs mmc 1 fat ${INSTALL_ROOTFS_FILENAME};
 	if test $? -eq 1; then
 		echo "[ERROR] Failed to update rootfs partition!";
 		echo "";