diff --git a/doc/Section_start.html b/doc/Section_start.html
index 00cb165ad2..f40c43d158 100644
--- a/doc/Section_start.html
+++ b/doc/Section_start.html
@@ -537,10 +537,12 @@ the input script is read.  "Name" is the variable name which can be a
 single character (referenced as $x in the input script) or a full
 string (referenced as ${abc}).  The value can be any string.  Using
 this command-line option is equivalent to putting the line "variable
-name index value" at the beginning of the input script.  See the
-<A HREF = "variable.html">variable</A> command for more info on defining variables
-and <A HREF = "Section_commands.html#3_2">this section</A> for more info on using
-variables in input scripts.
+name index value" at the beginning of the input script.  Defining a
+variable as a command-line argument overrides any setting for the same
+variable in the input script, since variables cannot be re-defined.
+See the <A HREF = "variable.html">variable</A> command for more info on defining
+variables and <A HREF = "Section_commands.html#3_2">this section</A> for more info
+on using variables in input scripts.
 </P>
 <HR>
 
diff --git a/doc/Section_start.txt b/doc/Section_start.txt
index aae316f666..922ebe329d 100644
--- a/doc/Section_start.txt
+++ b/doc/Section_start.txt
@@ -530,10 +530,12 @@ the input script is read.  "Name" is the variable name which can be a
 single character (referenced as $x in the input script) or a full
 string (referenced as $\{abc\}).  The value can be any string.  Using
 this command-line option is equivalent to putting the line "variable
-name index value" at the beginning of the input script.  See the
-"variable"_variable.html command for more info on defining variables
-and "this section"_Section_commands.html#3_2 for more info on using
-variables in input scripts.
+name index value" at the beginning of the input script.  Defining a
+variable as a command-line argument overrides any setting for the same
+variable in the input script, since variables cannot be re-defined.
+See the "variable"_variable.html command for more info on defining
+variables and "this section"_Section_commands.html#3_2 for more info
+on using variables in input scripts.
 
 :line