diff --git a/src/MTXClient.m b/src/MTXClient.m
index 256021d..29f3eb5 100644
--- a/src/MTXClient.m
+++ b/src/MTXClient.m
@@ -203,7 +203,11 @@ validateHomeserver(OFURL *homeserver)
 	MTXRequest *request = [self
 	    requestWithPath: @"/_matrix/client/r0/sync"];
 	unsigned long long timeoutMs = timeout * 1000;
-	request.query = [OFString stringWithFormat: @"timeout=%llu", timeoutMs];
+	OFMutableDictionary<OFString *, OFString *> *query =
+	    [OFMutableDictionary dictionaryWithObject: @(timeoutMs).stringValue
+					       forKey: @"timeout"];
+	query[@"since"] = [_storage nextBatchForDeviceID: _deviceID];
+	request.query = query;
 	[request performWithBlock: ^ (mtx_response_t response, int statusCode,
 				       id exception) {
 		if (exception != nil) {
diff --git a/src/MTXRequest.h b/src/MTXRequest.h
index 5bf3c93..412b3a3 100644
--- a/src/MTXRequest.h
+++ b/src/MTXRequest.h
@@ -73,7 +73,8 @@ typedef void (^mtx_request_block_t)(mtx_response_t _Nullable response,
 /**
  * @brief The query for the request.
  */
-@property (copy, nullable, nonatomic) OFString *query;
+@property (copy, nullable, nonatomic)
+    OFDictionary<OFString *, OFString *> *query;
 
 /**
  * @brief An optional body to send along with the request.
diff --git a/src/MTXRequest.m b/src/MTXRequest.m
index 8f9ec38..c48fbf2 100644
--- a/src/MTXRequest.m
+++ b/src/MTXRequest.m
@@ -97,7 +97,7 @@
 
 	OFMutableURL *requestURL = [[_homeserver mutableCopy] autorelease];
 	requestURL.path = _path;
-	requestURL.query = _query;
+	requestURL.queryDictionary = _query;
 
 	OFMutableDictionary *headers = [OFMutableDictionary dictionary];
 	headers[@"User-Agent"] = @"ObjMatrix";