diff --git a/tests/test-context.py b/tests/test-context.py
--- a/tests/test-context.py
+++ b/tests/test-context.py
@@ -77,7 +77,7 @@
 print(ctxb.status(ctxa))
 
 # test performing a diff on a memctx
-diffopts = diffutil.diffallopts(repo.ui, {'git': True})
+diffopts = diffutil.diffallopts(repo.ui, {b'git': True})
 for d in ctxb.diff(ctxa, opts=diffopts):
     printb(d, end=b'')