diff --git a/doc/src/dihedral_charmm.txt b/doc/src/dihedral_charmm.txt
index 918755ec3889678eacc5625f5b43bc401fb1a301..73dc67cdefef9bf3d853be18e4f4032b62e767d7 100644
--- a/doc/src/dihedral_charmm.txt
+++ b/doc/src/dihedral_charmm.txt
@@ -138,7 +138,15 @@ more instructions on how to use the accelerated styles effectively.
 
 [Restrictions:]
 
-This dihedral style can only be used if LAMMPS was built with the
+When using run_style "respa"_run_style.html, these dihedral styles
+must be assigned to the same r-RESPA level as {pair} or {outer}.
+
+When used in combination with CHARMM pair styles, the 1-4
+"special_bonds"_special_bonds.html scaling factors must be set to 0.0.
+Otherwise non-bonded contributions for these 1-4 pairs will be
+computed multiple times.
+
+These dihedral styles can only be used if LAMMPS was built with the
 MOLECULE package.  See the "Making
 LAMMPS"_Section_start.html#start_3 section for more info on packages.