diff --git a/build_library/build_image_util.sh b/build_library/build_image_util.sh
index 13bbbfd09f..e8e1b760e6 100755
--- a/build_library/build_image_util.sh
+++ b/build_library/build_image_util.sh
@@ -169,8 +169,7 @@ assert_image_size() {
 
   local size
   size=$(qemu-img info -f "${disk_type}" --output json "${disk_img}" | \
-      gawk 'match($0, /"virtual-size": ([0-9]+),/, val) {print val[1]}' ; \
-      exit ${PIPESTATUS[0]})
+    jq --raw-output '.["virtual-size"]' ; exit ${PIPESTATUS[0]})
   if [[ $? -ne 0 ]]; then
     die_notrace "assert failed: could not read image size"
   fi
diff --git a/build_library/grub_install.sh b/build_library/grub_install.sh
index 4861369083..59a6912323 100755
--- a/build_library/grub_install.sh
+++ b/build_library/grub_install.sh
@@ -108,7 +108,7 @@ if [[ ! -b "${LOOP_DEV}p1" ]]; then
             break
         fi
         warn "looback device node still ${LOOP_DEV}p1 missing, reprobing..."
-        blockdev --rereadpt ${LOOP_DEV}
+        sudo blockdev --rereadpt ${LOOP_DEV}
         sleep 0.5
     done
     if [[ ! -b "${LOOP_DEV}p1" ]]; then