diff --git a/src/github.com/matrix-org/dendrite/syncapi/sync/request.go b/src/github.com/matrix-org/dendrite/syncapi/sync/request.go
index 75b9f1050..9fa4900b0 100644
--- a/src/github.com/matrix-org/dendrite/syncapi/sync/request.go
+++ b/src/github.com/matrix-org/dendrite/syncapi/sync/request.go
@@ -34,7 +34,7 @@ type syncRequest struct {
 	userID        string
 	limit         int
 	timeout       time.Duration
-	since         *types.StreamPosition
+	since         *types.StreamPosition // nil means that no since token was supplied
 	wantFullState bool
 	log           *log.Entry
 }
@@ -70,8 +70,8 @@ func getTimeout(timeoutMS string) time.Duration {
 	return time.Duration(i) * time.Millisecond
 }
 
-// getSyncStreamPosition tries to pass a string taken from the API to a stream
-// position. If the string is empty then (nil, nil) is returned.
+// getSyncStreamPosition tries to pass a 'since' token taken from the API to a
+// stream position. If the string is empty then (nil, nil) is returned.
 func getSyncStreamPosition(since string) (*types.StreamPosition, error) {
 	if since == "" {
 		return nil, nil