diff --git a/logging/rtc_event_log/encoder/rtc_event_log_encoder_legacy.cc b/logging/rtc_event_log/encoder/rtc_event_log_encoder_legacy.cc
index 4e8529c..dac054c 100644
--- a/logging/rtc_event_log/encoder/rtc_event_log_encoder_legacy.cc
+++ b/logging/rtc_event_log/encoder/rtc_event_log_encoder_legacy.cc
@@ -365,8 +365,8 @@
     case RtcEvent::Type::GenericPacketReceived:
     case RtcEvent::Type::GenericPacketSent:
     case RtcEvent::Type::GenericAckReceived:
-      // These are unsupported in the old format.
-      break;
+      // These are unsupported in the old format, but shouldn't crash.
+      return "";
   }
 
   int event_type = static_cast<int>(event.GetType());