diff --git a/gitlab/mixins.py b/gitlab/mixins.py
index 9c00c324d..c2ba6d096 100644
--- a/gitlab/mixins.py
+++ b/gitlab/mixins.py
@@ -382,9 +382,12 @@ def save(self, **kwargs):
 
         # call the manager
         obj_id = self.get_id()
+        if isinstance(obj_id, (str)):
+            obj_id = obj_id.replace('/', '%2F')
         server_data = self.manager.update(obj_id, updated_data, **kwargs)
         if server_data is not None:
             self._update_attrs(server_data)
+        return server_data
 
 
 class ObjectDeleteMixin(object):
diff --git a/gitlab/v4/objects.py b/gitlab/v4/objects.py
index f6c09d9f2..b658b43c2 100644
--- a/gitlab/v4/objects.py
+++ b/gitlab/v4/objects.py
@@ -4937,7 +4937,53 @@ def upload(self, filename, filedata=None, filepath=None, **kwargs):
         data = self.manager.gitlab.http_post(url, files=file_info)
 
         return {"alt": data["alt"], "url": data["url"], "markdown": data["markdown"]}
+    
+    # see #56 - add file attachment features
+    @cli.register_custom_action("Project", ("filename", "filepath"))
+    @exc.on_http_error(exc.GitlabUploadError)
+    def wikiattachment(self, filename, filedata=None, filepath=None, **kwargs):
+        """Upload the specified file into the project Wiki.
+           https://docs.gitlab.com/ee/api/wikis.html#upload-an-attachment-to-the-wiki-repository
+
+        .. note::
+
+            Either ``filedata`` or ``filepath`` *MUST* be specified.
+
+        Args:
+            filename (str): The name of the file being uploaded
+            filedata (bytes): The raw data of the file being uploaded
+            filepath (str): The path to a local file to upload (optional)
+
+        Raises:
+            GitlabConnectionError: If the server cannot be reached
+            GitlabUploadError: If the file upload fails
+            GitlabUploadError: If ``filedata`` and ``filepath`` are not
+                specified
+            GitlabUploadError: If both ``filedata`` and ``filepath`` are
+                specified
+
+        Returns:
+            dict: A ``dict`` with the keys:
+                * ``alt`` - The alternate text for the upload
+                * ``url`` - The direct url to the uploaded file
+                * ``markdown`` - Markdown for the uploaded file
+        """
+        if filepath is None and filedata is None:
+            raise GitlabUploadError("No file contents or path specified")
+
+        if filedata is not None and filepath is not None:
+            raise GitlabUploadError("File contents and file path specified")
+
+        if filepath is not None:
+            with open(filepath, "rb") as f:
+                filedata = f.read()
+
+        url = "/projects/%(id)s/wikis/attachments" % {"id": self.id}
+        file_info = {"file": (filename, filedata)}
+        data = self.manager.gitlab.http_post(url, files=file_info)
 
+        return data
+    
     @cli.register_custom_action("Project", optional=("wiki",))
     @exc.on_http_error(exc.GitlabGetError)
     def snapshot(