diff --git a/src/wily/commands/build.py b/src/wily/commands/build.py
index 02b5b3b3..4d5a23da 100644
--- a/src/wily/commands/build.py
+++ b/src/wily/commands/build.py
@@ -134,6 +134,8 @@ def build(config: WilyConfig, archiver: Archiver, operators: List[Operator]) ->
 
                     # Copy the ir from any unchanged files from the prev revision
                     if not seed:
+                        # File names in result are platform dependent, so we convert
+                        # to Path and back to str.
                         files = {str(pathlib.Path(f)) for f in revision.tracked_files}
                         missing_indices = files - indices
                         # TODO: Check existence of file path.
@@ -156,9 +158,13 @@ def build(config: WilyConfig, archiver: Archiver, operators: List[Operator]) ->
                         for deleted in revision.deleted_files:
                             result.pop(deleted, None)
 
+                    # Add empty path for storing total aggregates
+                    dirs = [""]
+                    # Directory names in result are platform dependent, so we convert
+                    # to Path and back to str.
+                    dirs += [str(pathlib.Path(d)) for d in revision.tracked_dirs if d]
                     # Aggregate metrics across all root paths using the aggregate function in the metric
-                    # Note assumption is that nested dirs are listed after parent..
-                    dirs = {str(pathlib.Path(d)) for d in revision.tracked_dirs}
+                    # Note assumption is that nested dirs are listed after parent, hence sorting.
                     for root in sorted(dirs):
                         # find all matching entries recursively
                         aggregates = [