diff --git a/index.ts b/index.ts
index 7db70a4..682b5f5 100644
--- a/index.ts
+++ b/index.ts
@@ -1,6 +1,7 @@
 import fs = require('fs');
 import os = require('os');
 import path = require('path');
+import assert = require('assert');
 
 import ts = require('typescript');
 
@@ -171,12 +172,13 @@ namespace tss {
                 throw new Error(this.formatDiagnostics(allDiagnostics));
             }
 
-            if (output.outputFiles.length !== 1) {
-                const names = output.outputFiles.map(_ => _.name);
-                throw new Error(`Output should be only 1 file, but ${names.length} files: ${names.join(', ')}`);
+            if (output.outputFiles.length === 0) {
+                throw new Error('No output files');
             }
+            const file = output.outputFiles[0];
+            assert(/\.jsx?$/.test(file.name));
 
-            return output.outputFiles[0].text;
+            return file.text;
         }
 
         private formatDiagnostics(diagnostics: ts.Diagnostic[]): string {
diff --git a/test/test.js b/test/test.js
index 5fd883a..39d6011 100644
--- a/test/test.js
+++ b/test/test.js
@@ -267,10 +267,17 @@ describe('typescript-simple', function() {
       assert.equal(tss.compile(src, path.join('test', 'module.ts')), expected);
     });
 
-    it('compiles correct source with `types`', function() {
+    it('compiles source with `types`', function() {
       var tss = new TypeScriptSimple({types: ['node']});
       var src = "var x: number = 1;";
       var expected = 'var x = 1;' + eol;
       assert.equal(tss.compile(src), expected);
     });
+
+    it('compiles source with `declaratoin` enabled', function() {
+      var tss = new TypeScriptSimple({declaration: true});
+      var src = "var x: number = 1;";
+      var expected = 'var x = 1;' + eol;
+      assert.equal(tss.compile(src), expected);
+    });
 });