diff --git a/index.bs b/index.bs
index 3c393602..97c08daa 100644
--- a/index.bs
+++ b/index.bs
@@ -1630,7 +1630,7 @@ The sample rate used for computing offsets SHALL be the rate indicated by the [=
 - [=maximum block size=] SHALL be set to [=num_samples_per_frame=].
 - [=minimum frame size=] SHOULD be set to 0.
 - [=maximum frame size=] SHOULD be set to 0.
-- [=number of channels=] SHALL be set to 2. [=number of channels=] can be ignored because the real value can be determined from the [=Audio Element OBU=].
+- [=number of channels=] SHALL be set to 1. [=number of channels=] can be ignored because the real value can be determined from the [=Audio Element OBU=].
 - [=MD5 signature=] SHOULD be set to 0.
 
 The format of [=audio_frame()=] is [=FRAME=] of [[!FLAC]], which is composed of [=FRAME_HEADER=], followed by [=SUBFRAME=](s) (one [=SUBFRAME=] per channel) and followed by [=FRAME_FOOTER=].