diff --git a/dv/uvm/core_ibex/sim.py b/dv/uvm/core_ibex/sim.py
index a776c7b6..6d379246 100755
--- a/dv/uvm/core_ibex/sim.py
+++ b/dv/uvm/core_ibex/sim.py
@@ -436,7 +436,7 @@ def compare_test_run(test, idx, iss, output_dir, report):
     with open(report, 'a') as report_fd:
         test_name = test['test']
         elf = os.path.join(output_dir,
-                           'instr_gen/asm_test/{}.{}.o'.format(test_name, idx))
+                           'instr_gen/asm_test/{}_{}.o'.format(test_name, idx))
 
         logging.info("Comparing %s/DUT sim result : %s" % (iss, elf))