diff --git a/source/f90/doboson.f90 b/source/f90/doboson.f90
index 1dbff4422ef388432796e4358f55f82fa31228a3..535e448674d555c9e3d84fb782a1baeca475f967 100644
--- a/source/f90/doboson.f90
+++ b/source/f90/doboson.f90
@@ -132,7 +132,7 @@ subroutine doboson(t, width, gauss, asym, emin, emax, wmin, wmax, np, p, xout, y
       endif
     endif
 ! make a table of the response function
-    r1(1) = respon(0.0, alfa)
+    r1(1) = respon(0.0d0, alfa)
     r2(1) = r1(1)
     do i = 2, n
       x = (i - 1) * dwn