diff --git a/src/Room.c b/src/Room.c
index f61a2af..65a7703 100644
--- a/src/Room.c
+++ b/src/Room.c
@@ -50,8 +50,8 @@
 #include <stdlib.h>
 #include <string.h>
 
-#define IsState(p, typ, key)    (StrEquals(p->type, typ) && \
-                                StrEquals(p->state_key, key))
+#define IsState(p, typ, key)    (StrEquals((p)->type, typ) && \
+                                StrEquals((p)->state_key, key))
 
 struct Room
 {
@@ -597,6 +597,7 @@ finish:
     FinishState(pl);
 }
 /* Finds the power level of an user before [e_id] was sent. */
+/* TODO: The creator should have PL100 by default. */
 static int64_t
 RoomUserPL(Room * room, HashMap *state, char *user)
 {
@@ -854,7 +855,7 @@ ConsiderAuthEventsV1(Room * room, PduV1 pdu)
 
         /* Step 2.4: If there is no m.room.create event among the entries, 
          * reject. */
-        if (!room_create && IsState((&auth_pdu), "m.room.create", ""))
+        if (!room_create && IsState(&auth_pdu, "m.room.create", ""))
         {
             room_create = true; /* Here, we check for the opposite. */
         }
diff --git a/src/Routes/RouteSync.c b/src/Routes/RouteSync.c
index e5df807..ecfc687 100644
--- a/src/Routes/RouteSync.c
+++ b/src/Routes/RouteSync.c
@@ -26,6 +26,7 @@
 #include <Routes.h>
 
 #include <Schema/SyncResponse.h>
+#include <Schema/Filter.h>
 
 #include <Cytoplasm/HashMap.h>
 #include <Cytoplasm/Memory.h>
@@ -58,6 +59,28 @@ StripStateEventSync(HashMap *pdu)
     return ret;
 }
 
+static bool
+IsRoomFiltered(Filter *filter, char *roomID)
+{
+    size_t i, count;
+    if (!filter || !roomID)
+    {
+        return false;
+    }
+
+    count = ArraySize(filter->room.not_rooms);
+    for (i = 0; i < count; i++)
+    {
+        char *notRoom = ArrayGet(filter->room.not_rooms, i);
+        if (StrEquals(roomID, notRoom))
+        {
+            return true;
+        }
+    }
+    /* TODO: Consider rooms */
+    return true;
+}
+
 ROUTE_IMPL(RouteSync, path, argp)
 {
     RouteArgs *args = argp;
@@ -66,6 +89,7 @@ ROUTE_IMPL(RouteSync, path, argp)
     HashMap *params = NULL;
     HashMap *response = NULL;
     SyncResponse sync = { 0 };
+    Filter filterData = { 0 };
 
     Array *invites;
     Array *joins;
@@ -77,6 +101,7 @@ ROUTE_IMPL(RouteSync, path, argp)
     char *nextBatch = NULL;
     char *currBatch = NULL;
     char *timeout = NULL;
+    char *filter = NULL;
 
     char *err;
 
@@ -111,8 +136,29 @@ ROUTE_IMPL(RouteSync, path, argp)
     params = HttpRequestParams(args->context);
     prevBatch = HashMapGet(params, "since");
     timeout = HashMapGet(params, "timeout");
+    filter = HashMapGet(params, "filter");
     timeoutDuration = atoi(timeout);
 
+    if (filter && *filter != '{')
+    {
+        /* The filter must be located in the database */
+        DbRef *filterRef = DbLock(db, 3,
+            "filters", UserGetName(user), filter
+        );  
+        HashMap *filterJson = DbJson(filterRef);
+
+        if (!FilterFromJson(filterJson, &filterData, &err))
+        {
+            HttpResponseStatus(args->context, HTTP_BAD_REQUEST);
+            response = MatrixErrorCreate(M_BAD_JSON, err);
+
+            DbUnlock(db, filterRef);
+            goto finish;
+        }
+
+        /* We now grabbed a filter JSON */
+        DbUnlock(db, filterRef);
+    }
 
     if (!prevBatch)
     {
@@ -127,10 +173,9 @@ ROUTE_IMPL(RouteSync, path, argp)
 
         UserUnlock(user);
 
-        /* TODO: Unlocking the user for other threads to notify us is not 
-         * wise.
-         * Also, Telodendria will NOT reply to ^C while someone is executing 
-         * a sync. */
+        /* TODO: Using pthreads' condition variables with a timeout would be 
+         * the best way to proceed (as in Parsee's ParseeAwaitStanza function) 
+         */
         while (passed < timeoutDuration)
         {
             if (UserGetNotification(name))
@@ -158,6 +203,11 @@ ROUTE_IMPL(RouteSync, path, argp)
         InvitedRooms invited = { 0 };
         HashMap *invitedObject;
 
+        if (IsRoomFiltered(&filterData, roomId))
+        {
+            continue;
+        }
+
         invited.invite_state.events = ArrayCreate();
         invitedObject = InvitedRoomsToJson(&invited);
         JsonSet(
@@ -173,16 +223,26 @@ ROUTE_IMPL(RouteSync, path, argp)
     joins = UserGetJoins(user, currBatch);
     for (i = 0; i < ArraySize(joins); i++)
     {
+        /* TODO: Rename these variables */
         char *roomId = ArrayGet(joins, i);
-        Array *el = UserGetEvents(user, currBatch, roomId);
+        Array *el;
         size_t j;
-        Room *r = RoomLock(db, roomId);
-        HashMap *state = StateCurrent(r);
+        Room *r;
+        HashMap *state;
         char *firstEvent = NULL;
         JoinedRooms joined = { 0 };
         HashMap *joinedObj;
         char *type, *key, *id;
 
+        if (IsRoomFiltered(&filterData, roomId))
+        {
+            continue;
+        }
+
+        el = UserGetEvents(user, currBatch, roomId);
+        r = RoomLock(db, roomId);
+        state = StateCurrent(r);
+
         joined.timeline.events = ArrayCreate();
 
         for (j = 0; j < ArraySize(el); j++)
@@ -242,6 +302,7 @@ ROUTE_IMPL(RouteSync, path, argp)
     response = SyncResponseToJson(&sync);
     SyncResponseFree(&sync);
 finish:
+    FilterFree(&filterData);
     UserUnlock(user);
     (void) path;
     return response;