diff --git a/mercurial/utils/hashutil.py b/mercurial/utils/hashutil.py
new file mode 100644
--- /dev/null
+++ b/mercurial/utils/hashutil.py
@@ -0,0 +1,9 @@
+from __future__ import absolute_import
+
+import hashlib
+
+try:
+    from mercurial.thirdparty import sha1dc
+    sha1 = sha1dc.sha1
+except (ImportError, AttributeError):
+    sha1 = hashlib.sha1