diff --git a/tools/dtoc/src_scan.py b/tools/dtoc/src_scan.py
index 095fb6d..761164a 100644
--- a/tools/dtoc/src_scan.py
+++ b/tools/dtoc/src_scan.py
@@ -345,6 +345,11 @@
         This procedure will populate self._drivers and self._driver_aliases
         """
         for (dirpath, _, filenames) in os.walk(self._basedir):
+            rel_path = dirpath[len(self._basedir):]
+            if rel_path.startswith('/'):
+                rel_path = rel_path[1:]
+            if rel_path.startswith('build') or rel_path.startswith('.git'):
+                continue
             for fname in filenames:
                 if not fname.endswith('.c'):
                     continue
diff --git a/tools/dtoc/test_src_scan.py b/tools/dtoc/test_src_scan.py
index 25e4866..ada49fb 100644
--- a/tools/dtoc/test_src_scan.py
+++ b/tools/dtoc/test_src_scan.py
@@ -117,7 +117,9 @@
 
             fname_list = []
             add_file('fname.c')
+            add_file('.git/ignoreme.c')
             add_file('dir/fname2.c')
+            add_file('build-sandbox/ignoreme2.c')
 
             # Mock out scan_driver and check that it is called with the
             # expected files
@@ -127,7 +129,8 @@
             self.assertEqual(2, len(mocked.mock_calls))
             self.assertEqual(mock.call(fname_list[0]),
                              mocked.mock_calls[0])
-            self.assertEqual(mock.call(fname_list[1]),
+            # .git file should be ignored
+            self.assertEqual(mock.call(fname_list[2]),
                              mocked.mock_calls[1])
         finally:
             shutil.rmtree(indir)