diff --git a/Adjust/ADJUtil.m b/Adjust/ADJUtil.m
index 6a5d04515..a451c11db 100644
--- a/Adjust/ADJUtil.m
+++ b/Adjust/ADJUtil.m
@@ -228,7 +228,8 @@ + (NSString *) queryString:(NSDictionary *)parameters
     [pairs addObject:sentAtPair];
 
     if (queueSize > 0) {
-        NSString *queueSizeString = [NSString stringWithFormat:@"%ld", (NSInteger)queueSize];
+        unsigned long queueSizeNative = (unsigned long)queueSize;
+        NSString *queueSizeString = [NSString stringWithFormat:@"%lu", queueSizeNative];
         NSString *escapedQueueSize = [queueSizeString adjUrlEncode];
         NSString *queueSizePair = [NSString stringWithFormat:@"%@=%@", @"queue_size", escapedQueueSize];
         [pairs addObject:queueSizePair];