diff --git a/src/pytest_cov/engine.py b/src/pytest_cov/engine.py
index 64f5cafe..c9389197 100644
--- a/src/pytest_cov/engine.py
+++ b/src/pytest_cov/engine.py
@@ -450,6 +450,7 @@ def start(self):
             data_suffix=_data_suffix(f'w{self.nodeid}'),
             config_file=self.cov_config,
         )
+        self.cov._warn_unimported_source = False
         self.cov.start()
         self.set_env()
         super().start()