diff --git a/mercurial/mdiff.py b/mercurial/mdiff.py
--- a/mercurial/mdiff.py
+++ b/mercurial/mdiff.py
@@ -156,7 +156,7 @@ def diffline(revs, a, b, opts):
         parts.append(a)
     return ' '.join(parts) + '\n'
 
-def unidiff(a, ad, b, bd, fn1, fn2, r=None, opts=defaultopts):
+def unidiff(a, ad, b, bd, fn1, fn2, opts=defaultopts):
     def datetag(date, fn=None):
         if not opts.git and not opts.nodates:
             return '\t%s\n' % date
@@ -207,9 +207,6 @@ def unidiff(a, ad, b, bd, fn1, fn2, r=No
         if l[ln][-1] != '\n':
             l[ln] += "\n\ No newline at end of file\n"
 
-    if r:
-        l.insert(0, diffline(r, fn1, fn2, opts))
-
     return "".join(l)
 
 # creates a headerless unified diff
diff --git a/mercurial/patch.py b/mercurial/patch.py
--- a/mercurial/patch.py
+++ b/mercurial/patch.py
@@ -1746,17 +1746,17 @@ def trydiff(repo, revs, ctx1, ctx2, modi
                         dodiff = 'binary'
                 elif binary or nflag != oflag:
                     losedatafn(f)
-            if opts.git:
-                header.insert(0, mdiff.diffline(revs, join(a), join(b), opts))
 
         if dodiff:
+            if opts.git or revs:
+                header.insert(0, mdiff.diffline(revs, join(a), join(b), opts))
             if dodiff == 'binary':
                 text = mdiff.b85diff(to, tn)
             else:
                 text = mdiff.unidiff(to, date1,
                                     # ctx2 date may be dynamic
                                     tn, util.datestr(ctx2.date()),
-                                    join(a), join(b), revs, opts=opts)
+                                    join(a), join(b), opts=opts)
             if header and (text or len(header) > 1):
                 yield ''.join(header)
             if text: