diff --git a/content/docs/rfcs/13/README.md b/content/docs/rfcs/13/README.md
index d3cc0c59..35b1f7f6 100644
--- a/content/docs/rfcs/13/README.md
+++ b/content/docs/rfcs/13/README.md
@@ -38,7 +38,7 @@ Peers communicate with each other using a request / response API. The messages s
 ```protobuf
 message Index {
   bytes digest = 1;
-  float receivedTime = 2;
+  double receivedTime = 2;
 }
 
 message PagingInfo {
@@ -87,7 +87,7 @@ RPC call to query historical messages.
 
 - The `topics` field MUST indicate the list of topics to query.
 - `PagingInfo` holds the information required for pagination.  Its `pageSize` field indicates the number of  `WakuMessage`s to be included in the corresponding `HistoryResponse`. If the `pageSize` is zero then no pagination is required. If the `pageSize` exceeds a threshold then the threshold value shall be used instead. In the forward pagination request, the `messages` field of the `HistoryResponse` shall contain at maximum the `pageSize` amount of waku messages whose `Index` values are larger than the given `cursor` (and vise versa for the backward pagination). Note that the `cursor` of a `HistoryQuery` may be empty (e.g., for the initial query), as such, and depending on whether the  `direction` is `BACKWARD` or `FORWARD`  the last or the first `pageSize` waku messages shall be returned, respectively.
-The queried node MAY sort the `WakuMessage`s based on their `Index`, where the `receivedTime` constitutes the most significant part and the `digest` comes next, and then perform pagination on the sorted result. As such, the retrieved page contains an ordered list of `WakuMessage`s from the oldest message to the most recent one.
+The queried node MUST sort the `WakuMessage`s based on their `Index`, where the `receivedTime` constitutes the most significant part and the `digest` comes next, and then perform pagination on the sorted result. As such, the retrieved page contains an ordered list of `WakuMessage`s from the oldest message to the most recent one.
 
 ### HistoryResponse