diff --git a/metricbeat/module/system/test_system.py b/metricbeat/module/system/test_system.py
index e7a68e4f83a..35342c2c60b 100644
--- a/metricbeat/module/system/test_system.py
+++ b/metricbeat/module/system/test_system.py
@@ -488,6 +488,7 @@ def test_process_unix(self):
             process.pop("cgroup", None)
             process.pop("cmdline", None)
             process.pop("fd", None)
+            process.pop("num_threads", None)
 
             self.assertCountEqual(SYSTEM_PROCESS_FIELDS, process.keys())