diff --git a/runbot_merge/git.py b/runbot_merge/git.py
index 8f2732a8..36c5a1ab 100644
--- a/runbot_merge/git.py
+++ b/runbot_merge/git.py
@@ -263,12 +263,17 @@ class Repo:
                 f, _, local = f.rpartition("/")
                 # tree to update, `{tree}:` works as an alias for tree
                 lstree = repo.ls_tree(f"{tree}:{f}").stdout.splitlines(keepends=False)
-                new_tree = "".join(
+                new_tree = []
+                seen = False
+                for mode, typ, sha, name in map(methodcaller("split", None, 3), lstree):
+                    if name == local:
+                        sha = oid
+                        seen = True
                     # tab before name is critical to the format
-                    f"{mode} {typ} {oid if name == local else sha}\t{name}\n"
-                    for mode, typ, sha, name in map(methodcaller("split", None, 3), lstree)
-                )
-                oid = repo.with_config(input=new_tree, check=True).mktree().stdout.strip()
+                    new_tree.append(f"{mode} {typ} {sha}\t{name}\n")
+                if not seen:
+                    new_tree.append(f"100644 blob {oid}\t{local}\n")
+                oid = repo.with_config(input="".join(new_tree), check=True).mktree().stdout.strip()
             tree = oid
         return tree
 
diff --git a/runbot_merge/models/patcher.py b/runbot_merge/models/patcher.py
index 83e47d93..ef11588b 100644
--- a/runbot_merge/models/patcher.py
+++ b/runbot_merge/models/patcher.py
@@ -6,6 +6,7 @@ overhead, or FBI backdoors oh wait forget about that last one.
 """
 from __future__ import annotations
 
+import contextlib
 import logging
 import pathlib
 import re
@@ -179,7 +180,7 @@ class Patch(models.Model):
                         p.committer = f"{name} <{email}>"
                         p.commitdate = date
                 p.file_ids = File.concat(*(
-                    File.new({'name': m['file_from']})
+                    File.new({'name': m['file_to']})
                     for m in FILE_PATTERN.finditer(p.patch)
                 ))
                 p.message = r.message
@@ -233,7 +234,7 @@ class Patch(models.Model):
             has_files = False
             for m in FILE_PATTERN.finditer(patch.patch):
                 has_files = True
-                if m['file_from'] != m['file_to']:
+                if m['file_from'] != m['file_to'] and m['file_from'] != '/dev/null':
                     raise ValidationError("Only patches updating a file in place are supported, not creation, removal, or renaming.")
             if not has_files:
                 raise ValidationError("Patches should have files they patch, found none.")
@@ -321,25 +322,32 @@ class Patch(models.Model):
 
     def _apply_patch(self, r: git.Repo) -> str:
         p = self._parse_patch()
-        files = {}
         def reader(_r, f):
             return pathlib.Path(tmpdir, f).read_text(encoding="utf-8")
 
         prefix = 0
+        read = set()
+        patched = {}
         for m in FILE_PATTERN.finditer(p.patch):
-            if not prefix and m['prefix_a'] and m['prefix_b']:
+            if not prefix and (m['prefix_a'] or m['file_from'] == '/dev/null') and m['prefix_b']:
                 prefix = 1
 
-            files[m['file_to']] = reader
+            if m['file_from'] != '/dev/null':
+                read.add(m['file_from'])
+            patched[m['file_to']] = reader
 
         archiver = r.stdout(True)
         # if the parent is checked then we can't get rid of the kwarg and popen doesn't support it
         archiver._config.pop('check', None)
         archiver.runner = subprocess.Popen
-        with archiver.archive(self.target.name, *files) as out, \
-             tarfile.open(fileobj=out.stdout, mode='r|') as tf,\
+        with contextlib.ExitStack() as stack,\
              tempfile.TemporaryDirectory() as tmpdir:
-            tf.extractall(tmpdir)
+            # if there's no file to *update*, `archive` will extract the entire
+            # tree which is unnecessary
+            if read:
+                out = stack.enter_context(archiver.archive(self.target.name, *read))
+                tf = stack.enter_context(tarfile.open(fileobj=out.stdout, mode='r|'))
+                tf.extractall(tmpdir)
             patch = subprocess.run(
                 ['patch', f'-p{prefix}', '--directory', tmpdir, '--verbose'],
                 input=p.patch,
@@ -349,7 +357,7 @@ class Patch(models.Model):
             )
             if patch.returncode:
                 raise PatchFailure("\n---------\n".join(filter(None, [p.patch, patch.stdout.strip(), patch.stderr.strip()])))
-            new_tree = r.update_tree(self.target.name, files)
+            new_tree = r.update_tree(self.target.name, patched)
 
         sha = r.stdout().with_config(encoding='utf-8')\
             .show('--no-patch', '--pretty=%H', self.target.name)\
diff --git a/runbot_merge/tests/test_patching.py b/runbot_merge/tests/test_patching.py
index 46dc516f..9b57041c 100644
--- a/runbot_merge/tests/test_patching.py
+++ b/runbot_merge/tests/test_patching.py
@@ -15,7 +15,7 @@ Date:   2021-04-24T17:09:14Z
     whop whop
 
 diff --git a/b b/b
-index 000000000000..000000000000 100644
+index d00491fd7e5b..0cfbf08886fc 100644
 --- a/b
 +++ b/b
 @@ -1,1 +1,1 @@
@@ -35,7 +35,7 @@ whop whop
  1 file changed, 1 insertion(+), 1 deletion(-)
  
 diff --git a/b b/b
-index 000000000000..000000000000 100644
+index d00491fd7e5b..0cfbf08886fc 100644
 --- a/b
 +++ b/b
 @@ -1,1 +1,1 @@
@@ -47,7 +47,7 @@ index 000000000000..000000000000 100644
 
 # slightly different format than the one I got, possibly because older?
 FORMAT_PATCH_MAT = """\
-From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From 3000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
 From: 3 Discos Down <bar@example.org>
 Date: Sat, 24 Apr 2021 17:09:14 +0000
 Subject: [PATCH 1/1] [I18N] whop
@@ -58,7 +58,7 @@ whop whop
  1 file changed, 1 insertion(+), 1 deletion(-)
  
 diff --git b b
-index 000000000000..000000000000 100644
+index d00491fd7e5b..0cfbf08886fc 100644
 --- b
 +++ b
 @@ -1,1 +1,1 @@
@@ -268,3 +268,73 @@ def test_patch_conflict(env, project, repo, users):
     ), (
         False, '', [('active', 1, 0)]
     )]
+
+CREATE_FILE_FORMAT_PATCH = """\
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: 3 Discos Down <bar@example.org>
+Date: Sat, 24 Apr 2021 17:09:14 +0000
+Subject: [PATCH] [I18N] whop
+
+whop whop
+---
+ x | 1 +
+ 1 file changed, 1 insertion(+)
+ create mode 100644 b
+
+diff --git a/x b/x
+new file mode 100644
+index 000000000000..d00491fd7e5b
+--- /dev/null
++++ b/x
+@@ -0,0 +1 @@
++1
+-- 
+2.48.1
+"""
+
+CREATE_FILE_SHOW = """\
+commit 0000000000000000000000000000000000000000
+Author: 3 Discos Down <bar@example.org>
+Date:   2021-04-24T17:09:14Z
+
+    [I18N] whop
+    
+    whop whop
+
+diff --git a/x b/x
+new file mode 100644
+index 000000000000..d00491fd7e5b
+--- /dev/null
++++ b/x
+@@ -0,0 +1 @@
++1
+"""
+
+@pytest.mark.parametrize('patch', [
+    pytest.param(CREATE_FILE_SHOW, id='show'),
+    pytest.param(CREATE_FILE_FORMAT_PATCH, id='format-patch'),
+])
+def test_apply_creation(env, project, repo, users, patch):
+    assert repo.read_tree(repo.commit('master')) == {
+        'a': '2',
+        'b': '1\n',
+    }
+
+    env['runbot_merge.patch'].create({
+        'target': project.branch_ids.id,
+        'repository': project.repo_ids.id,
+        'patch': patch,
+    })
+    # trying to check the list of files doesn't work, even using web_read
+
+    env.run_crons()
+
+    HEAD = repo.commit('master')
+    assert repo.read_tree(HEAD) == {
+        'a': '2',
+        'b': '1\n',
+        'x': '1\n',
+    }
+    assert HEAD.message == "[I18N] whop\n\nwhop whop"
+    assert HEAD.author['name'] == "3 Discos Down"
+    assert HEAD.author['email'] == "bar@example.org"