diff --git a/doc/Section_errors.html b/doc/Section_errors.html
index 4bccb98b6e..e39f3de9d9 100644
--- a/doc/Section_errors.html
+++ b/doc/Section_errors.html
@@ -747,8 +747,10 @@ setting in order to use a middle setting.
 
 <DT><I>Cannot use atom vector in variable unless atom map exists</I> 
 
-<DD>Atom maps are on by default, but can be turned off be the atom_modify
-command. 
+<DD>Atom vectors require the ability to lookup an atom index, which
+is provided by an atom map.  An atom map does not exist (by default)
+for non-molecular problems.  Using the atom_modify map command will
+force an atom map to be created. 
 
 <DT><I>Cannot use both region, partial options in fix temp/rescale</I> 
 
diff --git a/doc/Section_errors.txt b/doc/Section_errors.txt
index 5ea01829a1..8e480043b4 100644
--- a/doc/Section_errors.txt
+++ b/doc/Section_errors.txt
@@ -744,8 +744,10 @@ The kspace style pppm cannot be used in 2d simulations.  You can use
 
 {Cannot use atom vector in variable unless atom map exists} :dt
 
-Atom maps are on by default, but can be turned off be the atom_modify
-command. :dd
+Atom vectors require the ability to lookup an atom index, which
+is provided by an atom map.  An atom map does not exist (by default)
+for non-molecular problems.  Using the atom_modify map command will
+force an atom map to be created. :dd
 
 {Cannot use both region, partial options in fix temp/rescale} :dt