diff --git a/doc/src/fix_spring_self.rst b/doc/src/fix_spring_self.rst
index f8354b17d7..a78e7575f8 100644
--- a/doc/src/fix_spring_self.rst
+++ b/doc/src/fix_spring_self.rst
@@ -106,7 +106,9 @@ invoked by the :doc:`minimize <minimize>` command.
 
 Restrictions
 """"""""""""
- none
+
+The KOKKOS version, *fix spring/self/kk* may only be used with a constant
+value of K, not a variable.
 
 Related commands
 """"""""""""""""