diff --git a/lib/downsam9.f90 b/lib/downsam9.f90
index 80131ab8b..4c18fe048 100644
--- a/lib/downsam9.f90
+++ b/lib/downsam9.f90
@@ -7,7 +7,7 @@ subroutine downsam9(id2,npts8,nsps8,newdat,nspsd,fpk,c2,nz2)
   use FFTW3
 
   include 'constants.f90'
-  integer*4 NMAX1
+  integer(C_SIZE_T) NMAX1
   parameter (NMAX1=604800)
   type(C_PTR) :: plan                        !Pointers plan for big FFT
   integer*2 id2(0:8*npts8-1)