diff --git a/doc/Section_errors.html b/doc/Section_errors.html
index e39f3de9d9..cb1ee97231 100644
--- a/doc/Section_errors.html
+++ b/doc/Section_errors.html
@@ -752,6 +752,13 @@ 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 fix tmd unless atom map exists</I> 
+
+<DD>TMD requires 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> 
 
 <DD>Self-explanatory. 
diff --git a/doc/Section_errors.txt b/doc/Section_errors.txt
index 8e480043b4..5daf9da640 100644
--- a/doc/Section_errors.txt
+++ b/doc/Section_errors.txt
@@ -749,6 +749,13 @@ 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 fix tmd unless atom map exists} :dt
+
+TMD requires 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
 
 Self-explanatory. :dd