diff --git a/include/Cache.h b/include/Cache.h
index 761c6060..7a626e12 100644
--- a/include/Cache.h
+++ b/include/Cache.h
@@ -44,26 +44,6 @@ from_json(const json &j, ReadReceiptKey &key)
         key.room_id  = j.at("room_id").get<std::string>();
 }
 
-//! Decribes a read receipt stored in cache.
-struct ReadReceiptValue
-{
-        std::string user_id;
-        uint64_t ts;
-};
-
-inline void
-to_json(json &j, const ReadReceiptValue &value)
-{
-        j = json{{"user_id", value.user_id}, {"ts", value.ts}};
-}
-
-inline void
-from_json(const json &j, ReadReceiptValue &value)
-{
-        value.user_id = j.at("user_id").get<std::string>();
-        value.ts      = j.at("ts").get<uint64_t>();
-}
-
 class Cache
 {
 public:
@@ -100,7 +80,7 @@ public:
         //! Retrieve all the read receipts for the given event id and room.
         //!
         //! Returns a map of user ids and the time of the read receipt in milliseconds.
-        using UserReceipts = std::multimap<uint64_t, std::string>;
+        using UserReceipts = std::multimap<uint64_t, std::string, std::greater<uint64_t>>;
         UserReceipts readReceipts(const QString &event_id, const QString &room_id);
 
         QByteArray image(const QString &url) const;
diff --git a/include/dialogs/ReadReceipts.h b/include/dialogs/ReadReceipts.h
index 42a9e1b7..8f860b46 100644
--- a/include/dialogs/ReadReceipts.h
+++ b/include/dialogs/ReadReceipts.h
@@ -37,7 +37,7 @@ public:
         explicit ReadReceipts(QWidget *parent = nullptr);
 
 public slots:
-        void addUsers(const std::multimap<uint64_t, std::string> &users);
+        void addUsers(const std::multimap<uint64_t, std::string, std::greater<uint64_t>> &users);
 
 protected:
         void paintEvent(QPaintEvent *event) override;
diff --git a/src/Cache.cc b/src/Cache.cc
index e27c4083..fd6a5ee9 100644
--- a/src/Cache.cc
+++ b/src/Cache.cc
@@ -25,11 +25,14 @@
 #include "Cache.h"
 #include "RoomState.h"
 
-static const std::string CURRENT_CACHE_FORMAT_VERSION("2017.12.10");
+static const std::string CURRENT_CACHE_FORMAT_VERSION("2018.01.14");
 
 static const lmdb::val NEXT_BATCH_KEY("next_batch");
 static const lmdb::val CACHE_FORMAT_VERSION_KEY("cache_format_version");
 
+using CachedReceipts = std::multimap<uint64_t, std::string, std::greater<uint64_t>>;
+using Receipts       = std::map<std::string, std::map<std::string, uint64_t>>;
+
 Cache::Cache(const QString &userId)
   : env_{nullptr}
   , stateDb_{0}
@@ -455,10 +458,10 @@ Cache::setInvites(const std::map<std::string, mtx::responses::InvitedRoom> &invi
         }
 }
 
-std::multimap<uint64_t, std::string>
+CachedReceipts
 Cache::readReceipts(const QString &event_id, const QString &room_id)
 {
-        std::multimap<uint64_t, std::string> receipts;
+        CachedReceipts receipts;
 
         ReadReceiptKey receipt_key{event_id.toStdString(), room_id.toStdString()};
         nlohmann::json json_key = receipt_key;
@@ -476,10 +479,11 @@ Cache::readReceipts(const QString &event_id, const QString &room_id)
 
                 if (res) {
                         auto json_response = json::parse(std::string(value.data(), value.size()));
-                        auto values        = json_response.get<std::vector<ReadReceiptValue>>();
+                        auto values        = json_response.get<std::map<std::string, uint64_t>>();
 
                         for (auto v : values)
-                                receipts.emplace(v.ts, v.user_id);
+                                // timestamp, user_id
+                                receipts.emplace(v.second, v.first);
                 }
 
         } catch (const lmdb::error &e) {
@@ -489,7 +493,6 @@ Cache::readReceipts(const QString &event_id, const QString &room_id)
         return receipts;
 }
 
-using Receipts = std::map<std::string, std::map<std::string, uint64_t>>;
 void
 Cache::updateReadReceipt(const std::string &room_id, const Receipts &receipts)
 {
@@ -511,7 +514,7 @@ Cache::updateReadReceipt(const std::string &room_id, const Receipts &receipts)
 
                         read_txn.commit();
 
-                        std::vector<ReadReceiptValue> saved_receipts;
+                        std::map<std::string, uint64_t> saved_receipts;
 
                         // If an entry for the event id already exists, we would
                         // merge the existing receipts with the new ones.
@@ -520,13 +523,12 @@ Cache::updateReadReceipt(const std::string &room_id, const Receipts &receipts)
                                   json::parse(std::string(prev_value.data(), prev_value.size()));
 
                                 // Retrieve the saved receipts.
-                                saved_receipts = json_value.get<std::vector<ReadReceiptValue>>();
+                                saved_receipts = json_value.get<std::map<std::string, uint64_t>>();
                         }
 
                         // Append the new ones.
                         for (auto event_receipt : event_receipts)
-                                saved_receipts.push_back(
-                                  ReadReceiptValue{event_receipt.first, event_receipt.second});
+                                saved_receipts.emplace(event_receipt.first, event_receipt.second);
 
                         // Save back the merged (or only the new) receipts.
                         nlohmann::json json_updated_value = saved_receipts;
diff --git a/src/dialogs/ReadReceipts.cc b/src/dialogs/ReadReceipts.cc
index feb382de..51470c67 100644
--- a/src/dialogs/ReadReceipts.cc
+++ b/src/dialogs/ReadReceipts.cc
@@ -96,7 +96,7 @@ ReadReceipts::ReadReceipts(QWidget *parent)
 }
 
 void
-ReadReceipts::addUsers(const std::multimap<uint64_t, std::string> &receipts)
+ReadReceipts::addUsers(const std::multimap<uint64_t, std::string, std::greater<uint64_t>> &receipts)
 {
         // We want to remove any previous items that have been set.
         userList_->clear();