diff --git a/spec.emu b/spec.emu
index 0f02e02..88be659 100644
--- a/spec.emu
+++ b/spec.emu
@@ -10,6 +10,7 @@ stage: 2
 location: https://github.com/tc39/proposal-immutable-arraybuffer
 shortname: proposal-immutable-arraybuffer
 contributors: Mark S. Miller, Richard Gibson
+markEffects: true
 </pre>
 
 <emu-clause id="sec-ecmascript-data-types-and-values" number="6">