diff --git a/modules/rtp_rtcp/source/video_rtp_depacketizer_h264.cc b/modules/rtp_rtcp/source/video_rtp_depacketizer_h264.cc
index 19ada0fa6f..49cc1af7d4 100644
--- a/modules/rtp_rtcp/source/video_rtp_depacketizer_h264.cc
+++ b/modules/rtp_rtcp/source/video_rtp_depacketizer_h264.cc
@@ -188,6 +188,7 @@ std::optional<VideoRtpDepacketizer::ParsedRtpPayload> ProcessStapAOrSingleNalu(
               << "Failed to parse PPS id and SPS id from PPS slice.";
           return std::nullopt;
         }
+        parsed_payload->video_header.is_first_packet_in_frame = true;
         break;
       }
       case H264::NaluType::kIdr:
@@ -212,12 +213,13 @@ std::optional<VideoRtpDepacketizer::ParsedRtpPayload> ProcessStapAOrSingleNalu(
       case H264::NaluType::kAud:
         parsed_payload->video_header.is_first_packet_in_frame = true;
         break;
+      case H264::NaluType::kSei:
+        parsed_payload->video_header.is_first_packet_in_frame = true;
+        break;
       // Slices below don't contain SPS or PPS ids.
       case H264::NaluType::kEndOfSequence:
       case H264::NaluType::kEndOfStream:
       case H264::NaluType::kFiller:
-      case H264::NaluType::kSei:
-        break;
       case H264::NaluType::kStapA:
       case H264::NaluType::kFuA:
         RTC_LOG(LS_WARNING) << "Unexpected STAP-A or FU-A received.";
diff --git a/modules/rtp_rtcp/source/video_rtp_depacketizer_h264_unittest.cc b/modules/rtp_rtcp/source/video_rtp_depacketizer_h264_unittest.cc
index d73d10f415..8f1d272b77 100644
--- a/modules/rtp_rtcp/source/video_rtp_depacketizer_h264_unittest.cc
+++ b/modules/rtp_rtcp/source/video_rtp_depacketizer_h264_unittest.cc
@@ -517,5 +517,30 @@ TEST(VideoRtpDepacketizerH264Test, AudSetsFirstPacketInFrame) {
   EXPECT_TRUE(parsed->video_header.is_first_packet_in_frame);
 }
 
+TEST(VideoRtpDepacketizerH264Test, PpsSetsFirstPacketInFrame) {
+  const uint8_t kPayload[] = {
+      0x08, 0x69, 0xFC, 0x0,  0x0,  0x3, 0x0,
+      0x7,  0xFF, 0xFF, 0xFF, 0xF6, 0x40  // PPS.
+  };
+
+  VideoRtpDepacketizerH264 depacketizer;
+  std::optional<VideoRtpDepacketizer::ParsedRtpPayload> parsed =
+      depacketizer.Parse(rtc::CopyOnWriteBuffer(kPayload));
+  ASSERT_TRUE(parsed);
+  EXPECT_TRUE(parsed->video_header.is_first_packet_in_frame);
+}
+
+TEST(VideoRtpDepacketizerH264Test, SeiSetsFirstPacketInFrame) {
+  const uint8_t kPayload[] = {
+      0x06, 0x05, 0x04, 0xDE, 0xAD, 0xBE, 0xEF, 0x80  // SEI.
+  };
+
+  VideoRtpDepacketizerH264 depacketizer;
+  std::optional<VideoRtpDepacketizer::ParsedRtpPayload> parsed =
+      depacketizer.Parse(rtc::CopyOnWriteBuffer(kPayload));
+  ASSERT_TRUE(parsed);
+  EXPECT_TRUE(parsed->video_header.is_first_packet_in_frame);
+}
+
 }  // namespace
 }  // namespace webrtc