diff --git a/css-typed-om/Overview.bs b/css-typed-om/Overview.bs
index 6d54d3d6..b8895a7a 100644
--- a/css-typed-om/Overview.bs
+++ b/css-typed-om/Overview.bs
@@ -561,6 +561,19 @@ The <dfn attribute for=CSSUnparsedValue>length</dfn> attribute indicates how man
 
 The <dfn for=CSSUnparsedValue>indexed getter</dfn> retrieves the string fragment or variable reference at the provided index.
 
+<div algorithm="CSSVariableReferenceValue.variable">
+    The <dfn attribute for=CSSVariableReferenceValue>variable</dfn> attribute
+    of a {{CSSVariableReferenceValue}} |this| must, on setting a
+    variable |variable|, perform the following steps:
+
+    1. If |variable| is not a [=custom property name string=], 
+        [=throw=] a {{TypeError}},
+        and exit this algorithm.
+
+    2. Otherwise, set |this|’s {{CSSVariableReferenceValue/variable}} internal slot
+        to |variable|.
+</div>
+
 <div algorithm>
     The <dfn constructor for=CSSVariableReferenceValue>CSSVariableReferenceValue(|variable|, |fallback|)</dfn> constructor must,
     when called,
@@ -574,6 +587,7 @@ The <dfn for=CSSUnparsedValue>indexed getter</dfn> retrieves the string fragment
         or `null` otherwise.
 </div>
 
+
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