diff --git a/lib/6to5/traversal/scope.js b/lib/6to5/traversal/scope.js
index af676612d5..49ec6b3959 100644
--- a/lib/6to5/traversal/scope.js
+++ b/lib/6to5/traversal/scope.js
@@ -195,7 +195,9 @@ Scope.prototype.register = function (node, reference, kind) {
   for (var key in ids) {
     var id = ids[key];
 
-    if (kind !== "hoisted") this.checkBlockScopedCollisions(key, id);
+    if (kind !== "hoisted" && kind !== "param") {
+      this.checkBlockScopedCollisions(key, id);
+    }
 
     this.registerType(key, id, node);
     this.bindings[key] = id;
@@ -274,10 +276,11 @@ Scope.prototype.crawl = function () {
 
   info = block._scopeInfo = {
     bindingKinds: {
-      "hoisted": object(),
-      "const":   object(),
-      "var":     object(),
-      "let":     object()
+      hoisted: object(),
+      "const": object(),
+      param:   object(),
+      "var":   object(),
+      "let":   object()
     },
 
     references: object(),
@@ -321,7 +324,7 @@ Scope.prototype.crawl = function () {
 
   if (t.isFunction(block)) {
     for (i = 0; i < block.params.length; i++) {
-      this.register(block.params[i], null, "let");
+      this.register(block.params[i], null, "param");
     }
     this.traverse(block.body, blockVariableVisitor, this);
   }