diff --git a/scripts/image_signing/sign_official_build.sh b/scripts/image_signing/sign_official_build.sh
index a3f7c98..83f31c6 100755
--- a/scripts/image_signing/sign_official_build.sh
+++ b/scripts/image_signing/sign_official_build.sh
@@ -714,7 +714,11 @@
   local esp_dir="$(make_temp_dir)"
   # We use the 'unsafe' variant because the EFI system partition is vfat type
   # and can be mounted in RW mode.
-  _mount_image_partition_retry "${image}" "${esp_partnum}" "${esp_dir}"
+  if ! _mount_image_partition_retry "${image}" "${esp_partnum}" \
+                                    "${esp_dir}"; then
+    error "Could not mount EFI partition for updating legacy bootloader cfg."
+    return 1
+  fi
 
   # If we can't find the dm parameter in the kernel config, bail out now.
   local kernel_config=$(grab_kernel_config "${image}" "${dm_partno}")