diff --git a/infer.cc b/infer.cc
index cf7c20636384417747933f4900ebc48e61c98a89..cff380ce262b74619db70e0f053a935be2140f16 100644
--- a/infer.cc
+++ b/infer.cc
@@ -27,6 +27,7 @@ Infer::Infer(float udLh, float ut, unsigned int uV) {
   dLh = udLh;
   t = ut;
   V = uV;
+  if (V<=0.0) V=1.0;
 
   if (fabs(t)<13.0) {
     Em_ = V * pow(2*M_PI,-2) * dLh * (sqr(t) - 1) * exp(-sqr(t)/2.0);