diff --git a/Documentation/user-notify.txt b/Documentation/user-notify.txt
index 3c922ed..5346b2e 100644
--- a/Documentation/user-notify.txt
+++ b/Documentation/user-notify.txt
@@ -125,6 +125,7 @@
 should be sent to the emails named in this section. Within a Git-style
 configuration file double quotes around complex operator values may
 need to be escaped, e.g. `filter = branch:\"^(maint|stable)-.*\"`.
+Single quotes are illegal and must be omitted.
 
 When sending email to a bare email address in a notify block, Gerrit
 Code Review ignores read access controls and assumes the administrator