diff --git a/SC1091.md b/SC1091.md
index e66788c..0c390b0 100644
--- a/SC1091.md
+++ b/SC1091.md
@@ -28,7 +28,7 @@ source somefile
 
 ShellCheck, for whichever reason, is not able to access the source file.
 
-This could be because you did not include it on the command line, did not use `shellcheck -x` to allow following other files, don't have permissions or a variety of other problems.
+This could be because you did not include it on the command line, did not use `shellcheck -x` (or specified `external-sources=true` in the [[.shellcheckrc|Directive#external-sources]]) to allow following other files don't have permissions or a variety of other problems.
 
 Feel free to ignore the error with a [[directive]].