diff --git a/index.src.html b/index.src.html
index 0a6ea365..2becfa8d 100644
--- a/index.src.html
+++ b/index.src.html
@@ -2073,7 +2073,10 @@
 run these steps:
 1. If {{AudioEncoderConfig/codec}} is not a <a>valid codec string</a>, return
     `false`.
-2. Return `true`.
+2. If the {{AudioEncoderConfig}} has a codec-specific extension and the corresponding 
+    registration in the [[WEBCODECS-CODEC-REGISTRY]] defines steps to check whether the
+    the extension is a valid extension, return the result of running those steps.
+3. Return `true`.
 
 <dl>
   <dt><dfn dict-member for=AudioEncoderConfig>codec</dfn></dt>
diff --git a/opus_codec_registration.src.html b/opus_codec_registration.src.html
index fa8018da..54dc1a09 100644
--- a/opus_codec_registration.src.html
+++ b/opus_codec_registration.src.html
@@ -105,7 +105,7 @@
 NOTE: Once the initialization has succeeded, any packet can be decoded at any
 time without error, but this might not result in the expected audio output.
 
-AudiEncoderConfig extensions {#audioencoderconfig-extensions}
+AudioEncoderConfig extensions {#audioencoderconfig-extensions}
 =============================================================
 
 <pre class='idl'>
@@ -131,16 +131,26 @@
 <xmp>
 dictionary OpusEncoderConfig {
   OpusBitstreamFormat format = "opus";
+  [EnforceRange] unsigned long frameDuration;
 };
 </xmp>
 </pre>
 
+To check if an {{OpusEncoderConfig}} is valid, run these steps:
+1. If {{OpusEncoderConfig/frameDuration}} is not a valid `ptime` value,
+    which is described in Section 6.1 of [[RFC7587]], return `false`.
+2. Return `true`.
+
 <dl>
   <dt><dfn dict-member for=OpusEncoderConfig>format</dfn></dt>
   <dd>
     Configures the format of output {{EncodedAudioChunk}}s. See
     {{OpusBitstreamFormat}}.
   </dd>
+  <dt><dfn dict-member for=OpusEncoderConfig>frameDuration</dfn></dt>
+  <dd>
+    Configures the frame duration, in milliseconds, of output {{EncodedAudioChunk}}s.
+  </dd>
 </dl>
 
 OpusBitstreamFormat {#opus-bitstream-format}