diff --git a/scripts/gen_run_tests.py b/scripts/gen_run_tests.py
index 1d70057f..39e2be24 100755
--- a/scripts/gen_run_tests.py
+++ b/scripts/gen_run_tests.py
@@ -31,6 +31,7 @@ possible_malloc_conf_opts = [
 ]
 
 print 'set -e'
+print 'if [ -f Makefile ] ; then make relclean ; fi'
 print 'autoconf'
 print 'rm -rf run_tests.out'
 print 'mkdir run_tests.out'