diff --git a/source/engine/mecanisms.js b/source/engine/mecanisms.js
index 6a4dfc870..36be57fb4 100644
--- a/source/engine/mecanisms.js
+++ b/source/engine/mecanisms.js
@@ -222,8 +222,24 @@ export let mecanismAllOf = (recurse, k, v) => {
 		/>
 	)
 
+
+	let evaluate = (situationGate, parsedRules, node) => {
+		let evaluateOne = child => evaluateNode(situationGate, parsedRules, child),
+			explanation = R.map(evaluateOne, node.explanation),
+			values = R.pluck('nodeValue', explanation),
+			nodeValue = R.any(R.equals(false), values)
+				? false // court-circuit
+				: R.any(R.equals(null), values) ? null : true
+
+		let collectMissing = node =>
+			node.nodeValue == null
+				? R.chain(collectNodeMissing, node.explanation)
+				: []
+		return rewriteNode(node, nodeValue, explanation, collectMissing)
+	}
+
 	return {
-		evaluate: evaluateArray(R.and, true),
+		evaluate: evaluate,
 		jsx,
 		explanation,
 		category: 'mecanism',