diff --git a/tests/stune/smoke_test_ramp.py b/tests/stune/smoke_test_ramp.py
index 7ab1bc0b85d1733d3161b5c62dee0c5784700cb3..e7a9d9eb3a32346fc43014b5c1f8e80a72329f16 100644
--- a/tests/stune/smoke_test_ramp.py
+++ b/tests/stune/smoke_test_ramp.py
@@ -61,7 +61,7 @@ class STune(LisaTest):
             # high load and it overutilizes the CPU
             rtapp_period = first_task_params[first_task_name]["params"]["period_ms"]
             task_start = boost_task_rtapp.index[0]
-            after_first_period = task_start + rtapp_period
+            after_first_period = task_start + (rtapp_period / 1000.)
             boost_task_rtapp = boost_task_rtapp.ix[after_first_period:]
 
             sched_load_scale = 1024