diff --git a/src/compiler/transformers/es2015.ts b/src/compiler/transformers/es2015.ts
index 2f00f66767f..e295ba11526 100644
--- a/src/compiler/transformers/es2015.ts
+++ b/src/compiler/transformers/es2015.ts
@@ -569,7 +569,7 @@ namespace ts {
         function visitThisKeyword(node: Node): Node {
             if (convertedLoopState) {
                 if (hierarchyFacts & HierarchyFacts.ArrowFunction) {
-                    // if the enclosing function is an ArrowFunction is then we use the captured 'this' keyword.
+                    // if the enclosing function is an ArrowFunction then we use the captured 'this' keyword.
                     convertedLoopState.containsLexicalThis = true;
                     return node;
                 }
@@ -1445,6 +1445,10 @@ namespace ts {
                             createVoidZero()
                         );
                         break;
+
+                    default:
+                        Debug.failBadSyntaxKind(node);
+                        break;
                 }
 
                 const captureNewTargetStatement = createVariableStatement(