diff --git a/mercurial/mdiff.py b/mercurial/mdiff.py
--- a/mercurial/mdiff.py
+++ b/mercurial/mdiff.py
@@ -84,7 +84,7 @@
         try:
             self.context = int(self.context)
         except ValueError:
-            raise error.Abort(
+            raise error.InputError(
                 _(b'diff context lines count must be an integer, not %r')
                 % pycompat.bytestr(self.context)
             )
diff --git a/tests/test-diff-unified.t b/tests/test-diff-unified.t
--- a/tests/test-diff-unified.t
+++ b/tests/test-diff-unified.t
@@ -46,7 +46,7 @@
 
   $ hg diff --nodates -U foo
   abort: diff context lines count must be an integer, not 'foo'
-  [255]
+  [10]
 
 
   $ hg diff --nodates -U 2
@@ -87,7 +87,7 @@
 
   $ hg --config diff.unified=foo diff --nodates
   abort: diff context lines count must be an integer, not 'foo'
-  [255]
+  [10]
 
 noprefix config and option