diff --git a/content/media/webaudio/BiquadFilterNode.cpp b/content/media/webaudio/BiquadFilterNode.cpp
index 47ea02f8c7a7..341620dd0569 100644
--- a/content/media/webaudio/BiquadFilterNode.cpp
+++ b/content/media/webaudio/BiquadFilterNode.cpp
@@ -298,41 +298,6 @@ BiquadFilterNode::WrapObject(JSContext* aCx)
 void
 BiquadFilterNode::SetType(BiquadFilterType aType)
 {
-  if (!Preferences::GetBool("media.webaudio.legacy.BiquadFilterNode")) {
-    // Do not accept the alternate enum values unless the legacy pref
-    // has been turned on.
-    switch (aType) {
-    case BiquadFilterType::_0:
-    case BiquadFilterType::_1:
-    case BiquadFilterType::_2:
-    case BiquadFilterType::_3:
-    case BiquadFilterType::_4:
-    case BiquadFilterType::_5:
-    case BiquadFilterType::_6:
-    case BiquadFilterType::_7:
-      // Do nothing in order to emulate setting an invalid enum value.
-      return;
-    default:
-      // Shut up the compiler warning
-      break;
-    }
-  }
-
-  // Handle the alternate enum values
-  switch (aType) {
-  case BiquadFilterType::_0: aType = BiquadFilterType::Lowpass; break;
-  case BiquadFilterType::_1: aType = BiquadFilterType::Highpass; break;
-  case BiquadFilterType::_2: aType = BiquadFilterType::Bandpass; break;
-  case BiquadFilterType::_3: aType = BiquadFilterType::Lowshelf; break;
-  case BiquadFilterType::_4: aType = BiquadFilterType::Highshelf; break;
-  case BiquadFilterType::_5: aType = BiquadFilterType::Peaking; break;
-  case BiquadFilterType::_6: aType = BiquadFilterType::Notch; break;
-  case BiquadFilterType::_7: aType = BiquadFilterType::Allpass; break;
-  default:
-    // Shut up the compiler warning
-    break;
-  }
-
   mType = aType;
   SendInt32ParameterToStream(BiquadFilterNodeEngine::TYPE,
                              static_cast<int32_t>(aType));
diff --git a/content/media/webaudio/test/test_biquadFilterNode.html b/content/media/webaudio/test/test_biquadFilterNode.html
index ace38b52de7d..3a0b60ad19da 100644
--- a/content/media/webaudio/test/test_biquadFilterNode.html
+++ b/content/media/webaudio/test/test_biquadFilterNode.html
@@ -55,8 +55,6 @@ addLoadEvent(function() {
     "allpass",
   ];
   for (var i = 0; i < types.length; ++i) {
-    filter.type = filter[types[i].toUpperCase()];
-    is(filter.type, types[i], "Correct alternname type enum value");
     filter.type = types[i];
   }
 
diff --git a/dom/webidl/BiquadFilterNode.webidl b/dom/webidl/BiquadFilterNode.webidl
index 7cf818333729..7103c4f6daf7 100644
--- a/dom/webidl/BiquadFilterNode.webidl
+++ b/dom/webidl/BiquadFilterNode.webidl
@@ -11,9 +11,6 @@
  */
 
 enum BiquadFilterType {
-  // Hack: Use numbers to support alternate enum values
-  "0", "1", "2", "3", "4", "5", "6", "7",
-
   "lowpass",
   "highpass",
   "bandpass",
@@ -38,26 +35,3 @@ interface BiquadFilterNode : AudioNode {
 
 };
 
-/*
- * The origin of this IDL file is
- * https://dvcs.w3.org/hg/audio/raw-file/tip/webaudio/specification.html#AlternateNames
- */
-partial interface BiquadFilterNode {
-    [Pref="media.webaudio.legacy.BiquadFilterNode"]
-    const unsigned short LOWPASS = 0;
-    [Pref="media.webaudio.legacy.BiquadFilterNode"]
-    const unsigned short HIGHPASS = 1;
-    [Pref="media.webaudio.legacy.BiquadFilterNode"]
-    const unsigned short BANDPASS = 2;
-    [Pref="media.webaudio.legacy.BiquadFilterNode"]
-    const unsigned short LOWSHELF = 3;
-    [Pref="media.webaudio.legacy.BiquadFilterNode"]
-    const unsigned short HIGHSHELF = 4;
-    [Pref="media.webaudio.legacy.BiquadFilterNode"]
-    const unsigned short PEAKING = 5;
-    [Pref="media.webaudio.legacy.BiquadFilterNode"]
-    const unsigned short NOTCH = 6;
-    [Pref="media.webaudio.legacy.BiquadFilterNode"]
-    const unsigned short ALLPASS = 7;
-};
-
diff --git a/testing/profiles/prefs_general.js b/testing/profiles/prefs_general.js
index dcd372caa1d5..9bfed49d4c24 100644
--- a/testing/profiles/prefs_general.js
+++ b/testing/profiles/prefs_general.js
@@ -145,7 +145,6 @@ user_pref("dom.gamepad.enabled", true);
 user_pref("dom.gamepad.non_standard_events.enabled", true);
 
 // Enable Web Audio legacy APIs
-user_pref("media.webaudio.legacy.BiquadFilterNode", true);
 user_pref("media.webaudio.legacy.PannerNode", true);
 user_pref("media.webaudio.legacy.OscillatorNode", true);