diff --git a/modules/audio_coding/acm2/acm_receiver.h b/modules/audio_coding/acm2/acm_receiver.h
index f07f8a9..1512656 100644
--- a/modules/audio_coding/acm2/acm_receiver.h
+++ b/modules/audio_coding/acm2/acm_receiver.h
@@ -203,11 +203,17 @@
   void GetDecodingCallStatistics(AudioDecodingCallStats* stats) const;
 
  private:
+  struct DecoderInfo {
+    int payload_type;
+    int sample_rate_hz;
+    int num_channels;
+    SdpAudioFormat sdp_format;
+  };
+
   uint32_t NowInTimestamp(int decoder_sampling_rate) const;
 
   rtc::CriticalSection crit_sect_;
-  absl::optional<std::pair<int, SdpAudioFormat>> last_decoder_
-      RTC_GUARDED_BY(crit_sect_);
+  absl::optional<DecoderInfo> last_decoder_ RTC_GUARDED_BY(crit_sect_);
   ACMResampler resampler_ RTC_GUARDED_BY(crit_sect_);
   std::unique_ptr<int16_t[]> last_audio_buffer_ RTC_GUARDED_BY(crit_sect_);
   CallStatistics call_stats_ RTC_GUARDED_BY(crit_sect_);