1 files changed, 1 insertions, 0 deletions
diff --git a/lib/compress.js b/lib/compress.js
index 216ca92a..647c97e1 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -1974,6 +1974,7 @@ merge(Compressor.prototype, {
             }
 
             function foldable(expr) {
+                if (expr instanceof AST_Assign && expr.right.single_use) return;
                 var lhs_ids = Object.create(null);
                 var marker = new TreeWalker(function(node) {
                     if (node instanceof AST_SymbolRef) lhs_ids[node.definition().id] = true;