diff --git a/mercurial/obsutil.py b/mercurial/obsutil.py
index f071b18e138252daad4709d10a73562f59b2b7bb_bWVyY3VyaWFsL29ic3V0aWwucHk=..0cf5f9312b33ef79965fe1f567d5cce77e16bcca_bWVyY3VyaWFsL29ic3V0aWwucHk= 100644
--- a/mercurial/obsutil.py
+++ b/mercurial/obsutil.py
@@ -417,7 +417,10 @@
 
     This is a first and basic implementation, with many shortcoming.
     """
-    diffopts = diffutil.diffallopts(leftctx.repo().ui, {b'git': True})
+    diffopts = diffutil.diffallopts(
+        leftctx.repo().ui,
+        {b'git': True, b'unified': 1},
+    )
 
     # Leftctx or right ctx might be filtered, so we need to use the contexts
     # with an unfiltered repository to safely compute the diff