diff --git a/build_library/grub.cfg b/build_library/grub.cfg
index 99433f23c0..79bb971e31 100644
--- a/build_library/grub.cfg
+++ b/build_library/grub.cfg
@@ -107,13 +107,37 @@ fi
 # Assemble the options applicable to all the kernels below
 set linux_cmdline="rootflags=rw mount.usrflags=ro consoleblank=0 $linux_root $linux_console $first_boot $oem_id $linux_append"
 
-menuentry "CoreOS default" --id=coreos {
-    gptprio.next -d usr -u usr_uuid
-    if [ "$usr_uuid" = "7130c94a-213a-4e5a-8e26-6cce9662f132" ]; then
-       linux$suf /coreos/vmlinuz-a @@MOUNTUSR@@=PARTUUID=$usr_uuid $linux_cmdline
-    else
-       linux$suf /coreos/vmlinuz-b @@MOUNTUSR@@=PARTUUID=$usr_uuid $linux_cmdline
+# Re-implement grub_abort() since no command exposes it.
+function abort {
+    echo
+    echo "Aborted. Press enter to exit GRUB."
+    read anything
+    exit
+}
+
+# Select the kernel and usr partition to boot.
+function gptprio {
+    # TODO: device name is no longer needed, should make it optional...
+    gptprio.next -d usr_device -u usr_uuid
+    if [ $? -ne 0 -o -z "$usr_uuid" ]; then
+        echo
+        echo "Reading or updating the GPT failed!"
+        echo "Please file a bug with any messages above to CoreOS:"
+        echo " https://github.com/coreos/bugs/issues"
+        abort
     fi
+
+    set gptprio_cmdline="@@MOUNTUSR@@=PARTUUID=$usr_uuid"
+    if [ "$usr_uuid" = "7130c94a-213a-4e5a-8e26-6cce9662f132" ]; then
+        set gptprio_kernel="/coreos/vmlinuz-a"
+    else
+        set gptprio_kernel="/coreos/vmlinuz-b"
+    fi
+}
+
+menuentry "CoreOS default" --id=coreos {
+    gptprio
+    linux$suf $gptprio_kernel $gptprio_cmdline $linux_cmdline
 }
 
 menuentry "CoreOS USR-A" --id=coreos-a {
diff --git a/build_library/grub_install.sh b/build_library/grub_install.sh
index 96c92a1755..b4cbba9598 100755
--- a/build_library/grub_install.sh
+++ b/build_library/grub_install.sh
@@ -39,7 +39,7 @@ GRUB_DIR="coreos/grub/${FLAGS_target}"
 GRUB_SRC="/usr/lib/grub/${FLAGS_target}"
 
 # Modules required to boot a standard CoreOS configuration
-CORE_MODULES=( normal search test fat part_gpt search_fs_uuid gzio search_part_label terminal gptprio configfile memdisk tar echo )
+CORE_MODULES=( normal search test fat part_gpt search_fs_uuid gzio search_part_label terminal gptprio configfile memdisk tar echo read )
 
 # Name of the core image, depends on target
 CORE_NAME=