diff --git a/.spellcheck-en-custom.txt b/.spellcheck-en-custom.txt
index 80d8261..3112cc8 100644
--- a/.spellcheck-en-custom.txt
+++ b/.spellcheck-en-custom.txt
@@ -37,3 +37,4 @@ libc
 url
 dir
 programmatically
+loopback
diff --git a/doc/01-usage.md b/doc/01-usage.md
index 303d8e1..756126e 100644
--- a/doc/01-usage.md
+++ b/doc/01-usage.md
@@ -105,6 +105,8 @@ $ sudo image-builder build minimal-raw
 # ... progress ...
 ```
 
+The `build` command requires root privileges in many cases as `image-builder` needs access to loopback devices and `mount`.
+
 By default the `build` command uses the same distribution and version as the host system, you can pass another distribution and version with the `--distro` argument:
 
 ```console