diff --git a/doc/run.html b/doc/run.html
index d3ac108fb9..da99cd1fb3 100644
--- a/doc/run.html
+++ b/doc/run.html
@@ -174,7 +174,12 @@ command:
 run will print the full timing summary, but these operations will be
 skipped for intermediate runs.
 </P>
-<P><B>Restrictions:</B> none
+<P><B>Restrictions:</B>
+</P>
+<P>The number of specified timesteps N must fit in a signed 32-bit
+integer, so you are limited to slightly more than 2 billion steps
+(2^31) in a single run.  However, you can perform successive runs to
+run a simulation for any number of steps (ok, up to 2^63 steps).
 </P>
 <P><B>Related commands:</B>
 </P>
diff --git a/doc/run.txt b/doc/run.txt
index 7561559c27..febf22777a 100644
--- a/doc/run.txt
+++ b/doc/run.txt
@@ -167,7 +167,12 @@ If the {pre} and {post} options are set to "no" when used with the
 run will print the full timing summary, but these operations will be
 skipped for intermediate runs.
 
-[Restrictions:] none
+[Restrictions:]
+
+The number of specified timesteps N must fit in a signed 32-bit
+integer, so you are limited to slightly more than 2 billion steps
+(2^31) in a single run.  However, you can perform successive runs to
+run a simulation for any number of steps (ok, up to 2^63 steps).
 
 [Related commands:]