diff --git a/tests/regression_tests/source_mcpl_file/gen_dummy_mcpl.c b/tests/regression_tests/source_mcpl_file/gen_dummy_mcpl.c
index f35a07fc44..61eea95c6f 100644
--- a/tests/regression_tests/source_mcpl_file/gen_dummy_mcpl.c
+++ b/tests/regression_tests/source_mcpl_file/gen_dummy_mcpl.c
@@ -52,6 +52,7 @@ int main(int argc, char **argv){
   /*the main particle loop*/
   particle=&Particle;
   int i;
+  srand(1234);
   for (i=0;i<batches*particles; i++){
     if(i%particles==0){
       printf("MCPL_test: generating batch number %d\n",i/particles);