diff --git a/doc/if.html b/doc/if.html
index 1821b9088c..d56baf9a9b 100644
--- a/doc/if.html
+++ b/doc/if.html
@@ -59,7 +59,8 @@ Boolean expression is FALSE, then no commands are executed.
 <P>The syntax for Boolean expressions is described below.
 </P>
 <P>Each command (t1, f1, e1, etc) can be any valid LAMMPS input script
-command.  If the command is more than one word, it must enclosed in
+command, except an <A HREF = "include.html">include</A> command, which is not
+allowed.  If the command is more than one word, it must enclosed in
 quotes, so it will be treated as a single argument, as in the examples
 above.
 </P>
diff --git a/doc/if.txt b/doc/if.txt
index bbbb85e05b..6c8a0fada1 100644
--- a/doc/if.txt
+++ b/doc/if.txt
@@ -56,7 +56,8 @@ Boolean expression is FALSE, then no commands are executed.
 The syntax for Boolean expressions is described below.
 
 Each command (t1, f1, e1, etc) can be any valid LAMMPS input script
-command.  If the command is more than one word, it must enclosed in
+command, except an "include"_include.html command, which is not
+allowed.  If the command is more than one word, it must enclosed in
 quotes, so it will be treated as a single argument, as in the examples
 above.