Index: head/release/amd64/mkisoimages.sh
===================================================================
--- head/release/amd64/mkisoimages.sh
+++ head/release/amd64/mkisoimages.sh
@@ -23,6 +23,8 @@
 # extra-bits-dir, if provided, contains additional files to be merged
 # into base-bits-dir as part of making the image.
 
+set -e
+
 if [ -z $ETDUMP ]; then
 	ETDUMP=etdump
 fi
Index: head/release/i386/mkisoimages.sh
===================================================================
--- head/release/i386/mkisoimages.sh
+++ head/release/i386/mkisoimages.sh
@@ -23,6 +23,8 @@
 # extra-bits-dir, if provided, contains additional files to be merged
 # into base-bits-dir as part of making the image.
 
+set -e
+
 if [ "$1" = "-b" ]; then
 	# This is highly x86-centric and will be used directly below.
 	bootable="-o bootimage=i386;$4/boot/cdboot -o no-emul-boot"
Index: head/release/powerpc/mkisoimages.sh
===================================================================
--- head/release/powerpc/mkisoimages.sh
+++ head/release/powerpc/mkisoimages.sh
@@ -23,6 +23,7 @@
 # extra-bits-dir, if provided, contains additional files to be merged
 # into base-bits-dir as part of making the image.
 
+set -e
 
 if [ "$1" = "-b" ]; then
 	bootable=1
Index: head/release/sparc64/mkisoimages.sh
===================================================================
--- head/release/sparc64/mkisoimages.sh
+++ head/release/sparc64/mkisoimages.sh
@@ -22,6 +22,8 @@
 # resulting ISO image, base-bits-dir contains the image contents and
 # extra-bits-dir, if provided, contains additional files to be merged
 # into base-bits-dir as part of making the image.
+set -e
+
 if [ $# -lt 3 ]; then
 	echo "Usage: $0 [-b] image-label image-name base-bits-dir [extra-bits-dir]" > /dev/stderr
 	exit 1