diff --git a/tools/amber2lmp/amber2lammps.py b/tools/amber2lmp/amber2lammps.py
index d6d5d3700c..c47a17cfe6 100644
--- a/tools/amber2lmp/amber2lammps.py
+++ b/tools/amber2lmp/amber2lammps.py
@@ -281,7 +281,7 @@ class Amber:
                     l.Dihedral_Coeffs[i][1] = 1
                 else:
                     l.Dihedral_Coeffs[i][1] = -1
-                l.Dihedral_Coeffs[i][2] = self.PN[i]
+                l.Dihedral_Coeffs[i][2] = int(self.PN[i])
 
             l.Atoms = []
             for i in range(self.NATOM):