diff --git a/src/KSPACE/pppm.cpp b/src/KSPACE/pppm.cpp
index 6add8b58b74dcf5a35ed1fd6cb1b8b75dda329d7..28dda4abfcc380a68c52a5f26656c58b0a72abc8 100644
--- a/src/KSPACE/pppm.cpp
+++ b/src/KSPACE/pppm.cpp
@@ -1268,6 +1268,7 @@ double PPPM::compute_qopt()
 double PPPM::estimate_ik_error(double h, double prd, bigint natoms)
 {
   double sum = 0.0;
+  if (natoms == 0) return 0.0;
   for (int m = 0; m < order; m++)
     sum += acons[order][m] * pow(h*g_ewald,2.0*m);
   double value = q2 * pow(h*g_ewald,(double)order) *