diff --git a/doc/velocity.html b/doc/velocity.html
index 69afb8b6ca..ac1a172896 100644
--- a/doc/velocity.html
+++ b/doc/velocity.html
@@ -76,7 +76,9 @@ not set.  Any of the vx,vy,vz velocity components can be specified as
 an equal-style or atom-style <A HREF = "variable.html">variable</A>.  If the value
 is a variable, it should be specified as v_name, where name is the
 variable name.  In this case, the variable will be evaluated, and its
-value used to determine the velocity component.
+value used to determine the velocity component.  Note that if a
+variable is used, the velocity it calculates must be in box units, not
+lattice units; see the discussion of the <I>units</I> keyword below.
 </P>
 <P>Equal-style variables can specify formulas with various mathematical
 functions, and include <A HREF = "thermo_style.html">thermo_style</A> command
diff --git a/doc/velocity.txt b/doc/velocity.txt
index b2f18c0dbe..2a606cf552 100644
--- a/doc/velocity.txt
+++ b/doc/velocity.txt
@@ -68,7 +68,9 @@ not set.  Any of the vx,vy,vz velocity components can be specified as
 an equal-style or atom-style "variable"_variable.html.  If the value
 is a variable, it should be specified as v_name, where name is the
 variable name.  In this case, the variable will be evaluated, and its
-value used to determine the velocity component.
+value used to determine the velocity component.  Note that if a
+variable is used, the velocity it calculates must be in box units, not
+lattice units; see the discussion of the {units} keyword below.
 
 Equal-style variables can specify formulas with various mathematical
 functions, and include "thermo_style"_thermo_style.html command