diff --git a/src/formats/h26x.cc b/src/formats/h26x.cc
index c677e92..e6a77c2 100644
--- a/src/formats/h26x.cc
+++ b/src/formats/h26x.cc
@@ -335,6 +335,13 @@ rtp_error_t uvgrtp::formats::h26x::push_media_frame(sockaddr_in& addr, sockaddr_
     if (!data || !data_len)
         return RTP_INVALID_VALUE;
 
+    /* This is the first call of init_transaction. It generates a new RTP timestamp. The init_transaction() calls
+       below will use the same RTP timestamp. */
+    if ((ret = fqueue_->init_transaction(data)) != RTP_OK) {
+        UVG_LOG_ERROR("Invalid frame queue or failed to initialize transaction!");
+        return ret;
+    }
+
     size_t payload_size = rtp_ctx_->get_payload_size();
 
     // find all the locations of NAL units using Start Code Lookup (SCL)
@@ -366,10 +373,6 @@ rtp_error_t uvgrtp::formats::h26x::push_media_frame(sockaddr_in& addr, sockaddr_
 
     if (should_aggregate && !do_not_aggr) // an aggregate packet is possible
     {
-        if ((ret = fqueue_->init_transaction(data)) != RTP_OK) {
-            UVG_LOG_ERROR("Invalid frame queue or failed to initialize transaction!");
-            return ret;
-        }
 
         // use aggregation function that also may just send the packets as Single NAL units 
         // if aggregates have not been implemented
@@ -685,7 +688,7 @@ rtp_error_t uvgrtp::formats::h26x::packet_handler(void* args, int rce_flags, uin
     
     // first we check that this packet does not belong to an access unit that has been dropped by garbage collection
     if (dropped_ts_.find(frame->header.timestamp) != dropped_ts_.end()) {
-        UVG_LOG_DEBUG("Received an RTP packet belonging to an old, dropped access unit! Timestamp: %lu, seq: %u",
+        UVG_LOG_DEBUG("Received an RTP packet belonging to an old, dropped access unit! Timestamp: %u, seq: %u",
             frame->header.timestamp, frame->header.seq);
         (void)uvgrtp::frame::dealloc_frame(frame); // free fragment memory
         return RTP_GENERIC_ERROR;
diff --git a/test/test_4_formats.cpp b/test/test_4_formats.cpp
index 1cef8bf..17ebe5a 100644
--- a/test/test_4_formats.cpp
+++ b/test/test_4_formats.cpp
@@ -692,7 +692,7 @@ TEST(FormatTests, h264_aggregation)
     std::this_thread::sleep_for(std::chrono::milliseconds(200));
 
     std::cout << "H264: Received/expected: " << aggr_received << "/" << expected << std::endl;
-    ASSERT_TRUE(aggr_received >= expected/3);
+    ASSERT_TRUE(aggr_received == expected);
     cleanup_ms(sess, sender);
     cleanup_ms(sess, receiver);
     cleanup_sess(ctx, sess);
@@ -739,7 +739,7 @@ TEST(FormatTests, h265_aggregation)
     std::this_thread::sleep_for(std::chrono::milliseconds(200));
 
     std::cout << "H265: Received/expected: " << aggr_received << "/" << expected << std::endl;
-    ASSERT_TRUE(aggr_received >= expected/3);
+    ASSERT_TRUE(aggr_received == expected);
     cleanup_ms(sess, sender);
     cleanup_ms(sess, receiver);
     cleanup_sess(ctx, sess);
@@ -786,7 +786,54 @@ TEST(FormatTests, h266_aggregation)
     std::this_thread::sleep_for(std::chrono::milliseconds(200));
 
     std::cout << "H266: Received/expected: " << aggr_received << "/" << expected << std::endl;
-    ASSERT_TRUE(aggr_received >= expected/3);
+    ASSERT_TRUE(aggr_received == expected);
+    cleanup_ms(sess, sender);
+    cleanup_ms(sess, receiver);
+    cleanup_sess(ctx, sess);
+}
+
+TEST(FormatTests, h265_disable_aggr)
+{
+    std::cout << "Testing RTP_H26X_DO_NOT_AGGR flag" << std::endl;
+    uvgrtp::context ctx;
+    uvgrtp::session* sess = ctx.create_session(LOCAL_ADDRESS);
+
+    uvgrtp::media_stream* sender = nullptr;
+    uvgrtp::media_stream* receiver = nullptr;
+
+    aggr_received = 0;
+    int expected = 3;
+
+    if (sess)
+    {
+        sender = sess->create_stream(SEND_PORT, RECEIVE_PORT, RTP_FORMAT_H265, RCE_NO_FLAGS);
+        receiver = sess->create_stream(RECEIVE_PORT, SEND_PORT, RTP_FORMAT_H265, RCE_NO_FLAGS);
+        receiver->install_receive_hook(nullptr, aggr_receive_hook);
+    }
+
+    int rtp_flags = RTP_NO_FLAGS;
+    rtp_format_t format = RTP_FORMAT_H265;
+    int test_runs = 1;
+
+    std::vector<size_t> test_sizes = { 100, 200, 300 };
+
+    size_t total_size = 0;
+    std::unique_ptr<uint8_t[]> test_frame = std::unique_ptr<uint8_t[]>(new uint8_t[700]);
+
+    for (auto& size : test_sizes)
+    {
+        int nal_type = 8;
+        std::unique_ptr<uint8_t[]> nal_unit = create_test_packet(format, nal_type, true, size, rtp_flags);
+        memcpy(test_frame.get() + total_size, nal_unit.get(), size);
+        total_size += size;
+    }
+    if (sender->push_frame(std::move(test_frame), total_size, RTP_H26X_DO_NOT_AGGR) != RTP_OK) {
+        std::cout << "Failed to send test packet!" << std::endl;
+    }
+    std::this_thread::sleep_for(std::chrono::milliseconds(200));
+
+    std::cout << "H265: Received/expected: " << aggr_received << "/" << expected << std::endl;
+    ASSERT_TRUE(aggr_received == expected);
     cleanup_ms(sess, sender);
     cleanup_ms(sess, receiver);
     cleanup_sess(ctx, sess);