diff --git a/lib/6to5/traversal/scope.js b/lib/6to5/traversal/scope.js
index f2f9691554..d8190a282d 100644
--- a/lib/6to5/traversal/scope.js
+++ b/lib/6to5/traversal/scope.js
@@ -418,7 +418,7 @@ var programReferenceVisitor = {
       state.addGlobal(node);
     } else if (t.isLabeledStatement(node)) {
       state.addGlobal(node);
-    } else if (t.isAssignmentExpression(node) || t.isUpdateExpression(node)) {
+    } else if (t.isAssignmentExpression(node) || t.isUpdateExpression(node) || (t.isUnaryExpression(node) && node.operator === "delete")) {
       scope.registerBindingReassignment(node);
     }
   }
diff --git a/lib/6to5/types/index.js b/lib/6to5/types/index.js
index f11ed92e33..d65f5811f0 100644
--- a/lib/6to5/types/index.js
+++ b/lib/6to5/types/index.js
@@ -608,6 +608,7 @@ t.getBindingIdentifiers = function (node) {
 };
 
 t.getBindingIdentifiers.keys = {
+  UnaryExpression: ["argument"],
   AssignmentExpression: ["left"],
   ImportBatchSpecifier: ["name"],
   VariableDeclarator: ["id"],