diff --git a/shellcheck.1.md b/shellcheck.1.md
index c212fa7..9d4be0f 100644
--- a/shellcheck.1.md
+++ b/shellcheck.1.md
@@ -52,7 +52,13 @@ not warn at all, as `ksh` supports decimals in arithmetic contexts.
 
 **-V**,\ **--version**
 
-:   Print version and exit.
+:   Print version information and exit.
+
+**-x**,\ **-external-sources**
+
+:   Follow 'source' statements even when the file is not specified as input.
+    By default, `shellcheck` will only follow files specified on the command
+    line. This option allows following any file the script may `source`.
 
 # FORMATS