diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 663825f1e84..c7317908273 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -15917,6 +15917,7 @@ namespace ts {
             //     export_opt   AmbientDeclaration
             //
             if (node.kind === SyntaxKind.InterfaceDeclaration ||
+                node.kind === SyntaxKind.TypeAliasDeclaration ||
                 node.kind === SyntaxKind.ImportDeclaration ||
                 node.kind === SyntaxKind.ImportEqualsDeclaration ||
                 node.kind === SyntaxKind.ExportDeclaration ||