diff --git a/spec.emu b/spec.emu
index 7a76f8d..d2b3cc9 100644
--- a/spec.emu
+++ b/spec.emu
@@ -830,6 +830,7 @@ contributors: Mark S. Miller, Richard Gibson
           <emu-alg>
             1. Let _O_ be the *this* value.
             1. Perform ? RequireInternalSlot(_O_, [[ArrayBufferData]]).
+            1. If IsSharedArrayBuffer(_O_) is *true*, throw a *TypeError* exception.
             1. Return IsImmutableBuffer(_O_).
           </emu-alg>
         </emu-clause>