diff --git a/src/transformer/descriptor/helper/helper.ts b/src/transformer/descriptor/helper/helper.ts
index e79fa7793..f5dd14465 100644
--- a/src/transformer/descriptor/helper/helper.ts
+++ b/src/transformer/descriptor/helper/helper.ts
@@ -6,12 +6,22 @@ type Declaration = ts.InterfaceDeclaration | ts.ClassDeclaration | ts.TypeAliasD
 type ImportDeclaration = ts.ImportEqualsDeclaration | ts.ImportOrExportSpecifier | ts.ImportClause;
 
 export namespace TypescriptHelper {
-  export function IsLiteralOrPrimitive(typeNode: ts.Node): boolean {
-    return ts.isLiteralTypeNode(typeNode) ||
-            typeNode.kind === ts.SyntaxKind.StringKeyword ||
-            typeNode.kind === ts.SyntaxKind.BooleanKeyword ||
-            typeNode.kind === ts.SyntaxKind.NumberKeyword ||
-            typeNode.kind === ts.SyntaxKind.ArrayType;
+  export interface PrimitiveTypeNode extends ts.TypeNode {
+    kind: ts.SyntaxKind.LiteralType | ts.SyntaxKind.NumberKeyword | ts.SyntaxKind.ObjectKeyword | ts.SyntaxKind.BooleanKeyword | ts.SyntaxKind.StringKeyword | ts.SyntaxKind.ArrayType;
+  }
+
+  export function IsLiteralOrPrimitive(typeNode: ts.Node): typeNode is PrimitiveTypeNode {
+    switch (typeNode.kind) {
+      case ts.SyntaxKind.LiteralType:
+      case ts.SyntaxKind.NumberKeyword:
+      case ts.SyntaxKind.ObjectKeyword:
+      case ts.SyntaxKind.BooleanKeyword:
+      case ts.SyntaxKind.StringKeyword:
+      case ts.SyntaxKind.ArrayType:
+        return true;
+    }
+
+    return false;
   }
 
   export function GetDeclarationFromNode(node: ts.Node): ts.Declaration {
@@ -119,22 +129,6 @@ export namespace TypescriptHelper {
     return !!((symbol.flags & ts.SymbolFlags.Alias) || (symbol.flags & ts.SymbolFlags.AliasExcludes));
   }
 
-  export interface RuntimeTypeNode extends ts.TypeNode {
-    kind: ts.SyntaxKind.NumberKeyword | ts.SyntaxKind.ObjectKeyword | ts.SyntaxKind.BooleanKeyword | ts.SyntaxKind.StringKeyword | ts.SyntaxKind.UndefinedKeyword;
-  }
-
-  export function isLiteralRuntimeTypeNode(typeNode: ts.TypeNode): typeNode is RuntimeTypeNode {
-    switch (typeNode.kind) {
-      case ts.SyntaxKind.NumberKeyword:
-      case ts.SyntaxKind.ObjectKeyword:
-      case ts.SyntaxKind.BooleanKeyword:
-      case ts.SyntaxKind.StringKeyword:
-        return true;
-    }
-
-    return false;
-  }
-
   function isImportExportDeclaration(declaration: ts.Declaration): declaration is ImportDeclaration  {
     return ts.isImportEqualsDeclaration(declaration) || ts.isImportOrExportSpecifier(declaration) || ts.isImportClause(declaration);
   }
diff --git a/src/transformer/descriptor/method/method.ts b/src/transformer/descriptor/method/method.ts
index 1bddcf351..6e0eaeda8 100644
--- a/src/transformer/descriptor/method/method.ts
+++ b/src/transformer/descriptor/method/method.ts
@@ -54,7 +54,7 @@ function CreateTypeEquality(signatureType: ts.TypeNode | undefined, primaryDecla
     );
   }
 
-  if (TypescriptHelper.isLiteralRuntimeTypeNode(signatureType)) {
+  if (TypescriptHelper.IsLiteralOrPrimitive(signatureType)) {
     return ts.createStrictEquality(
       ts.createTypeOf(identifier),
       signatureType ? ts.createStringLiteral(signatureType.getText()) : ts.createVoidZero(),