diff --git a/lib/models/room.js b/lib/models/room.js
index eff95ed79..ad586ff3f 100644
--- a/lib/models/room.js
+++ b/lib/models/room.js
@@ -375,13 +375,15 @@ Room.prototype.recalculate = function(userId) {
 
         var readReceiptsForEvent = this.getReceiptsForEvent(e);
 
-        readReceiptsForEvent.forEach(function(receipt) {
-            if (receipt.type !== "m.read") { return; }
-            if (usersFound[receipt.userId]) { return; }
+        for (var receiptIt = 0; receiptIt < readReceiptsForEvent.length; ++receiptIt) {
+            var receipt = readReceiptsForEvent[receiptIt];
+            if (receipt.type !== "m.read") { continue; }
+
+            if (usersFound[receipt.userId]) { continue; }
 
             // Then this is the receipt we keep for this user
             usersFound[receipt.userId] = 1;
-        });
+        }
 
         if (e.sender && usersFound[e.sender.userId] === undefined) {
             // no receipt yet for this sender, so we synthesize one.