diff --git a/mercurial/patch.py b/mercurial/patch.py
--- a/mercurial/patch.py
+++ b/mercurial/patch.py
@@ -14,7 +14,7 @@ import email.Generator
 import email.Parser
 
 from i18n import _
-from node import hex, nullid, short
+from node import hex, short
 import base85, mdiff, scmutil, util, diffhelpers, copies, encoding, error
 import context
 
@@ -1662,7 +1662,7 @@ def trydiff(repo, revs, ctx1, ctx2, modi
 
     def gitindex(text):
         if not text:
-            return hex(nullid)
+            text = ""
         l = len(text)
         s = util.sha1('blob %d\0' % l)
         s.update(text)
diff --git a/tests/test-diff-upgrade.t b/tests/test-diff-upgrade.t
--- a/tests/test-diff-upgrade.t
+++ b/tests/test-diff-upgrade.t
@@ -183,7 +183,7 @@ git=auto: regular diff for regular files
   % git=auto: git diff for newbinary
   diff --git a/newbinary b/newbinary
   new file mode 100644
-  index 0000000000000000000000000000000000000000..f76dd238ade08917e6712764a16a22005a50573d
+  index e69de29bb2d1d6434b8b29ae775ad8c2e48c5391..f76dd238ade08917e6712764a16a22005a50573d
   GIT binary patch
   literal 1
   Ic${MZ000310RR91
@@ -200,7 +200,7 @@ git=auto: regular diff for regular files
   % git=auto: git diff for rmbinary
   diff --git a/rmbinary b/rmbinary
   deleted file mode 100644
-  index f76dd238ade08917e6712764a16a22005a50573d..0000000000000000000000000000000000000000
+  index f76dd238ade08917e6712764a16a22005a50573d..e69de29bb2d1d6434b8b29ae775ad8c2e48c5391
   GIT binary patch
   literal 0
   Hc$@<O00001
diff --git a/tests/test-git-export.t b/tests/test-git-export.t
--- a/tests/test-git-export.t
+++ b/tests/test-git-export.t
@@ -113,7 +113,7 @@ Binary diff:
   $ cat b.diff
   diff --git a/binfile.bin b/binfile.bin
   new file mode 100644
-  index 0000000000000000000000000000000000000000..37ba3d1c6f17137d9c5f5776fa040caf5fe73ff9
+  index e69de29bb2d1d6434b8b29ae775ad8c2e48c5391..37ba3d1c6f17137d9c5f5776fa040caf5fe73ff9
   GIT binary patch
   literal 593
   zc$@)I0<QguP)<h;3K|Lk000e1NJLTq000mG000mO0ssI2kdbIM00009a7bBm000XU