diff --git a/perfact/zodbsync/tests/test_sync.py b/perfact/zodbsync/tests/test_sync.py
index 5ddd767..d1e9348 100644
--- a/perfact/zodbsync/tests/test_sync.py
+++ b/perfact/zodbsync/tests/test_sync.py
@@ -2329,3 +2329,27 @@ def test_layer_info_datafs(self):
                 )
             self.run('record', '/')
             assert getattr(self.app.blob, 'zodbsync_layer', None) is None
+
+    def test_fail_when_meta_is_missing(self):
+        """
+        Check that playing back a structure where no layer has a meta file for
+        a given folder does not work.
+        """
+        root = f'{self.repo.path}/__root__'
+        os.mkdir(f'{root}/newfolder')
+        os.mkdir(f'{root}/newobj')
+        with open(f'{root}/newobj/__source__.py', 'w'):
+            pass
+        with pytest.raises(AssertionError):
+            self.run('playback', '/')
+
+    def test_fail_when_meta_missing_layers(self):
+        """
+        Check that playing back a structure where no layer has a meta file for
+        a given folder does not work (multi-layer).
+        """
+        with self.addlayer() as layer:
+            os.mkdir(f'{self.repo.path}/__root__/newfolder')
+            os.mkdir(f'{layer}/workdir/__root__/newfolder')
+            with pytest.raises(AssertionError):
+                self.run('playback', '/')
diff --git a/perfact/zodbsync/zodbsync.py b/perfact/zodbsync/zodbsync.py
index 907b951..e626f8c 100644
--- a/perfact/zodbsync/zodbsync.py
+++ b/perfact/zodbsync/zodbsync.py
@@ -79,7 +79,7 @@ def mod_read(obj=None, onerrorstop=False, default_owner=None,
 
     if meta_type not in known_types:
         if onerrorstop:
-            assert False, "Unsupported type: %s" % meta_type
+            raise AssertionError(f"Unsupported type: {meta_type}")
         else:
             meta['unsupported'] = meta_type
             return meta
@@ -139,7 +139,8 @@ def mod_write(data, parent=None, obj_id=None, override=False, root=None,
     temp_obj = None
     # ID exists? Check for type
     if obj and obj.meta_type != meta_type:
-        assert override, "Type mismatch for object " + repr(data)
+        if not override:
+            raise AssertionError(f"Type mismatch for object {data!r}")
         contents = obj_contents(obj)
         if contents:
             # Rename so we can cut+paste the children
@@ -322,10 +323,11 @@ def start_transaction(self, note=''):
         # Log in as a manager
         uf = self.app.acl_users
         user = uf.getUser(self.manager_user).__of__(uf)
-        assert user is not None, (
-            'User %s is not available in database. Perhaps you need to set'
-            ' create_manager_user in config.py?' % self.manager_user
-        )
+        if user is None:
+            raise AssertionError(
+                f'User {self.manager_user} is not available in database.'
+                ' Perhaps you need to set create_manager_user in config.py?'
+            )
 
         self.logger.info('Using user %s' % self.manager_user)
         AccessControl.SecurityManagement.newSecurityManager(None, user)
@@ -424,7 +426,8 @@ def fs_pathinfo(self, path):
             'layeridx': None,
         }
         path = path.lstrip('/')
-        children = set()
+        candidates = set()  # subfolders on any layer
+        children = set()  # those with a __meta__ file on a some layer
         for idx, layer in enumerate(layers):
             fspath = os.path.join(layer['workdir'], self.site, path)
             if not os.path.isdir(fspath):
@@ -437,8 +440,14 @@ def fs_pathinfo(self, path):
             for entry in os.listdir(fspath):
                 if entry in children or entry.startswith('__'):
                     continue
+                candidates.add(entry)
                 if os.path.exists(os.path.join(fspath, entry, '__meta__')):
                     children.add(entry)
+        missing = candidates - children
+        if missing:
+            raise AssertionError(
+                f"No __meta__ file on any layer: {path}/{children}"
+            )
 
         result['children'] = sorted(children)
         return result
@@ -632,11 +641,13 @@ def fs_parse(self, fspath, data=None):
         if data is None:
             data = self.fs_read(fspath)
 
-        assert 'meta' in data, 'Missing meta file: ' + fspath
+        if 'meta' not in data:
+            raise AssertionError(f"Missing meta file: {fspath}")
         src_fnames = data.get('src_fnames', [])
-        assert len(src_fnames) <= 1, (
-            "Multiple source files in " + fspath
-        )
+        if len(src_fnames) > 1:
+            raise AssertionError(
+                f"Multiple source files in {fspath}"
+            )
         result = dict(literal_eval(data['meta']))
         if src_fnames:
             src_fname = src_fnames[0]