diff --git a/api/audio_codecs/audio_encoder.cc b/api/audio_codecs/audio_encoder.cc
index 2c1111814e..cd4d2000d2 100644
--- a/api/audio_codecs/audio_encoder.cc
+++ b/api/audio_codecs/audio_encoder.cc
@@ -110,9 +110,4 @@ ANAStats AudioEncoder::GetANAStats() const {
   return ANAStats();
 }
 
-absl::optional<std::pair<TimeDelta, TimeDelta>>
-AudioEncoder::GetFrameLengthRange() const {
-  return absl::nullopt;
-}
-
 }  // namespace webrtc
diff --git a/api/audio_codecs/audio_encoder.h b/api/audio_codecs/audio_encoder.h
index c6e572c87b..fd2d948863 100644
--- a/api/audio_codecs/audio_encoder.h
+++ b/api/audio_codecs/audio_encoder.h
@@ -244,7 +244,7 @@ class AudioEncoder {
   // information. This is used to calculated the full bitrate range, including
   // overhead.
   virtual absl::optional<std::pair<TimeDelta, TimeDelta>> GetFrameLengthRange()
-      const;
+      const = 0;
 
  protected:
   // Subclasses implement this to perform the actual encoding. Called by