diff --git a/repo_trace.py b/repo_trace.py
index ee224ea..d8ed583 100644
--- a/repo_trace.py
+++ b/repo_trace.py
@@ -57,10 +57,10 @@
     _TRACE_TO_STDERR = True
 
 
-def SetTrace():
-    """Enables tracing."""
+def SetTrace(value: bool = True) -> None:
+    """Enables by default, or disables tracing."""
     global _TRACE
-    _TRACE = True
+    _TRACE = value
 
 
 def _SetTraceFile(quiet):
diff --git a/tests/conftest.py b/tests/conftest.py
index ce3c3d6..c760468 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -26,6 +26,7 @@
 @pytest.fixture(autouse=True)
 def disable_repo_trace(tmp_path):
     """Set an environment marker to relax certain strict checks for test code."""  # noqa: E501
+    repo_trace.SetTrace(False)
     repo_trace._TRACE_FILE = str(tmp_path / "TRACE_FILE_from_test")
 
 
diff --git a/tests/test_repo_trace.py b/tests/test_repo_trace.py
index 3ec540b..7b938a6 100644
--- a/tests/test_repo_trace.py
+++ b/tests/test_repo_trace.py
@@ -25,6 +25,9 @@
     """Check Trace behavior."""
     content = "git chicken"
 
+    # Enable trace for the test, in case users have it disabled.
+    monkeypatch.setattr(repo_trace, "_TRACE", True)
+
     with repo_trace.Trace(content, first_trace=True):
         pass
     first_trace_size = os.path.getsize(repo_trace._TRACE_FILE)