diff --git a/synapse/rest/client/v2_alpha/sync.py b/synapse/rest/client/v2_alpha/sync.py
index a883c8add..eb7351621 100644
--- a/synapse/rest/client/v2_alpha/sync.py
+++ b/synapse/rest/client/v2_alpha/sync.py
@@ -112,9 +112,9 @@ class SyncRestServlet(RestServlet):
         full_state = parse_boolean(request, "full_state", default=False)
 
         logger.debug(
-            "/sync: user=%r, timeout=%r, since=%r,"
-            " set_presence=%r, filter_id=%r, device_id=%r"
-            % (user, timeout, since, set_presence, filter_id, device_id)
+            "/sync: user=%r, timeout=%r, since=%r, "
+            "set_presence=%r, filter_id=%r, device_id=%r",
+            user, timeout, since, set_presence, filter_id, device_id
         )
 
         request_key = (user, timeout, since, filter_id, full_state, device_id)
diff --git a/synapse/rest/media/v1/preview_url_resource.py b/synapse/rest/media/v1/preview_url_resource.py
index 0c68c3aad..13782d312 100644
--- a/synapse/rest/media/v1/preview_url_resource.py
+++ b/synapse/rest/media/v1/preview_url_resource.py
@@ -117,8 +117,8 @@ class PreviewUrlResource(DirectServeResource):
                 pattern = entry[attrib]
                 value = getattr(url_tuple, attrib)
                 logger.debug(
-                    ("Matching attrib '%s' with value '%s' against" " pattern '%s'")
-                    % (attrib, value, pattern)
+                    "Matching attrib '%s' with value '%s' against" " pattern '%s'",
+                    attrib, value, pattern
                 )
 
                 if value is None:
@@ -186,7 +186,7 @@ class PreviewUrlResource(DirectServeResource):
 
         media_info = yield self._download_url(url, user)
 
-        logger.debug("got media_info of '%s'" % media_info)
+        logger.debug("got media_info of '%s'", media_info)
 
         if _is_media(media_info["media_type"]):
             file_id = media_info["filesystem_id"]
@@ -254,7 +254,7 @@ class PreviewUrlResource(DirectServeResource):
                         og["og:image:width"] = dims["width"]
                         og["og:image:height"] = dims["height"]
                     else:
-                        logger.warn("Couldn't get dims for %s" % og["og:image"])
+                        logger.warn("Couldn't get dims for %s", og["og:image"])
 
                     og["og:image"] = "mxc://%s/%s" % (
                         self.server_name,
@@ -268,7 +268,7 @@ class PreviewUrlResource(DirectServeResource):
             logger.warn("Failed to find any OG data in %s", url)
             og = {}
 
-        logger.debug("Calculated OG for %s as %s" % (url, og))
+        logger.debug("Calculated OG for %s as %s", url, og)
 
         jsonog = json.dumps(og)
 
@@ -297,7 +297,7 @@ class PreviewUrlResource(DirectServeResource):
 
         with self.media_storage.store_into_file(file_info) as (f, fname, finish):
             try:
-                logger.debug("Trying to get url '%s'" % url)
+                logger.debug("Trying to get url '%s'", url)
                 length, headers, uri, code = yield self.client.get_file(
                     url, output_stream=f, max_size=self.max_spider_size
                 )