diff --git a/gh_actions_exporter/metrics.py b/gh_actions_exporter/metrics.py
index 22518ff..4dbd1ec 100644
--- a/gh_actions_exporter/metrics.py
+++ b/gh_actions_exporter/metrics.py
@@ -187,6 +187,6 @@ def handle_job_duration(self, webhook: WebHook):
                         - webhook.workflow_job.started_at.timestamp())
             self.job_duration.labels(**labels).observe(duration)
         elif webhook.workflow_job.status == "in_progress":
-            duration = (webhook.workflow_job.steps[0].completed_at.timestamp()
+            duration = (webhook.workflow_job.steps[0].started_at.timestamp()
                         - webhook.workflow_job.started_at.timestamp())
             self.job_start_duration.labels(**labels).observe(duration)
diff --git a/tests/api/conftest.py b/tests/api/conftest.py
index 6558bb9..2bf3da7 100644
--- a/tests/api/conftest.py
+++ b/tests/api/conftest.py
@@ -64,8 +64,8 @@ def workflow_job():
                     "status": "in_progress",
                     "conclusion": None,
                     "number": 1,
-                    "started_at": "2021-11-29T14:46:57Z",
-                    "completed_at": "2021-11-29T14:54:57Z"
+                    "started_at": "2021-11-29T14:50:57Z",
+                    "completed_at": None
                 }
             ],
             "labels": ["github-hosted"]
diff --git a/tests/api/test_job.py b/tests/api/test_job.py
index b5bc923..e10a0d8 100644
--- a/tests/api/test_job.py
+++ b/tests/api/test_job.py
@@ -24,7 +24,7 @@ def test_workflow_job_in_progress(client, workflow_job, headers):
         if 'inprogress_count_total{' in line:
             assert "1.0" in line
         if 'start_duration_seconds_sum{' in line:
-            assert '480.0' in line
+            assert '240.0' in line
 
 
 def test_workflow_job_label_self_hosted(client, workflow_job, headers):
@@ -56,4 +56,4 @@ def test_multiple_job_runs(client, workflow_job, headers):
         if 'job_total_count_total{' in line:
             assert '1.0' in line
         if 'job_start_duration_seconds_sum{' in line:
-            assert '480.0' in line
+            assert '240.0' in line