diff --git a/tmux.1 b/tmux.1
index ac9797b5..9fd247d0 100644
--- a/tmux.1
+++ b/tmux.1
@@ -5578,7 +5578,8 @@ for example
 .Ql #{session_name} .
 The possible variables are listed in the table below, or the name of a
 .Nm
-option may be used for an option's value.
+option may be used for an option's value, or the name of an environment
+variable.
 Some variables have a shorter alias such as
 .Ql #S ;
 .Ql ##