diff --git a/dev_tools/incremental_coverage.py b/dev_tools/incremental_coverage.py
index 044ac8e8411..ba004fe7667 100644
--- a/dev_tools/incremental_coverage.py
+++ b/dev_tools/incremental_coverage.py
@@ -20,6 +20,7 @@
 from dev_tools import env_tools, shell_tools
 
 IGNORED_FILE_PATTERNS = [
+    r'^(.+/)?conftest\.py$',
     r'^dev_tools/.+',  # Environment-heavy code.
     r'^.+_pb2(_grpc)?\.py$',  # Auto-generated protobuf code.
     r'^(.+/)?setup\.py$',  # Installation code.