1 files changed, 4 insertions, 0 deletions
diff --git a/coverage/data.py b/coverage/data.py
index 6d49f71..30119d9 100644
--- a/coverage/data.py
+++ b/coverage/data.py
@@ -207,6 +207,10 @@ class CoverageData(object):
         for filename, arcs in arc_data.items():
             self.arcs.setdefault(filename, {}).update(arcs)
 
+    def touch_file(self, filename):
+        """Ensure that `filename` appears in the data, empty if needed."""
+        self.lines.setdefault(filename, {})
+
     def executed_files(self):
         """A list of all files that had been measured as executed."""
         return list(self.lines.keys())