diff --git a/index.js b/index.js
index 757d53a..2c2a773 100644
--- a/index.js
+++ b/index.js
@@ -40,14 +40,20 @@ exports.compile = function compile(source, options) {
 };
 
 var validOptions = {
-  "compilerOptions": "object",
-  "filePath": "string",
-  "moduleName": "string",
-  "typings": "array"
+  "compilerOptions": "Object",
+  "filePath": "String",
+  "moduleName": "String",
+  "typings": "Array"
 };
 var validOptionsMsg = "Valid options are" +
   "compilerOptions, filePath, moduleName, and typings";
 
+function checkType(option, optionName) {
+  if (! option) return true;
+
+  return option.constructor.name === validOptions[optionName];
+}
+
 function validateAndConvertOptions(options) {
   if (! options) return;
 
@@ -59,7 +65,7 @@ function validateAndConvertOptions(options) {
           validOptionsMsg);
       }
 
-      if (typeof options[option] !== validOptions[option]) {
+      if (! checkType(options[option], option)) {
         throw new Error(option + " should be of type " +
           validOptions[option]);
       }
diff --git a/package.json b/package.json
index a70ccc2..0343f5c 100644
--- a/package.json
+++ b/package.json
@@ -1,7 +1,7 @@
 {
   "name": "meteor-typescript",
   "author": "@barbatus",
-  "version": "0.5.2",
+  "version": "0.5.5",
   "license": "MIT",
   "description": "TypeScript wrapper package for use with Meteor",
   "keywords": [
diff --git a/tests/ts.spec.js b/tests/ts.spec.js
index 675f51d..2c183ac 100644
--- a/tests/ts.spec.js
+++ b/tests/ts.spec.js
@@ -1,53 +1,85 @@
 var meteorTS = require("../index");
 
-describe("meteor-typescript", function() {
+describe("meteor-typescript -> ", function() {
 
-  var testCodeLine = "export const foo = 'foo'";
+  describe("testing exports and options -> ", function() {
+    var testCodeLine = "export const foo = 'foo'";
 
-  it("should compile with defaults", function() {
-    var result = meteorTS.compile(testCodeLine);
-    expect(result.code.indexOf("exports.foo")).toEqual(0);
-  });
+    it("should compile with defaults", function() {
+      var result = meteorTS.compile(testCodeLine);
+      expect(result.code.indexOf("exports.foo")).toEqual(0);
+    });
 
-  it("should throw on wrong option", function() {
-    var test = function() {
-      meteorTS.compile(testCodeLine, {
-        "wrong": true
-      });
-    };
-    expect(test).toThrow();
-  });
+    it("should throw on wrong option", function() {
+      var test = function() {
+        meteorTS.compile(testCodeLine, {
+          "wrong": true
+        });
+      };
+      expect(test).toThrow();
+    });
 
-  it("should recognize preset options", function() {
-    var result = meteorTS.compile(testCodeLine, {
-      compilerOptions: {
-        module: "system"
-      }
+    it("should allow null options", function() {
+      var result = meteorTS.compile(testCodeLine, {
+        compilerOptions: null,
+        typings: undefined
+      });
+      expect(result.code).not.toBeNull();
     });
-    expect(result.code.indexOf("System.register")).toEqual(0);
-  });
 
-  it("should add module with moduleName name when moduleName is set",
-    function() {
+    it("should recognize preset options", function() {
       var result = meteorTS.compile(testCodeLine, {
         compilerOptions: {
           module: "system"
-        },
-        moduleName: "fooModule"
+        }
       });
-      expect(result.code.indexOf("System.register(\"fooModule\""))
-        .toEqual(0);
+      expect(result.code).toContain("System.register");
     });
 
-  it("should throw on wrong compiler option", function() {
-    var test = function() {
-        meteorTS.compile(testCodeLine, {
+    it("should add module with moduleName name when moduleName is set",
+      function() {
+        var result = meteorTS.compile(testCodeLine, {
           compilerOptions: {
-          module: "wrong"
-        }
+            module: "system"
+          },
+          moduleName: "fooModule"
+        });
+        expect(result.code.indexOf("System.register(\"fooModule\""))
+          .toEqual(0);
       });
-    };
-    expect(test).toThrow();
+
+    it("should throw on wrong compiler option", function() {
+      var test = function() {
+          meteorTS.compile(testCodeLine, {
+            compilerOptions: {
+            module: "wrong"
+          }
+        });
+      };
+      expect(test).toThrow();
+    });
+  });
+
+  describe("testing diagnostics and typings -> ", function() {
+    var codeLineWithImport = "import {api} from 'lib'; export const foo = 'foo'";
+
+    it("should contain a semantic error when some module undefined", function() {
+      var result = meteorTS.compile(codeLineWithImport);
+
+      expect(result.diagnostics.semanticErrors).not.toBeNull();
+      expect(result.diagnostics.semanticErrors.length).toEqual(1);
+      var error = result.diagnostics.semanticErrors[0].message;
+      expect(error).toContain("Cannot find module 'lib'");
+    });
+
+    it("declaration file with module declaration should remove an error", function() {
+      var result = meteorTS.compile(codeLineWithImport, {
+        typings: ["typings/lib.d.ts"]
+      });
+
+      expect(result.diagnostics.semanticErrors).not.toBeNull();
+      expect(result.diagnostics.semanticErrors.length).toEqual(0);
+    });
   });
 
 });
diff --git a/tests/typings/lib.d.ts b/tests/typings/lib.d.ts
new file mode 100644
index 0000000..1c44253
--- /dev/null
+++ b/tests/typings/lib.d.ts
@@ -0,0 +1,3 @@
+declare module "lib" {
+  export let api = {};
+}
diff --git a/typescript.js b/typescript.js
index 1e656dc..69dc7f7 100644
--- a/typescript.js
+++ b/typescript.js
@@ -32,7 +32,7 @@ exports.compile = function compile(fileContent, options) {
   var compilerHost = _.extend({}, defaultHost, customHost);
   var fileNames = [filePath];
   if (options.typings) {
-    fileNames.concat(options.typings);
+    fileNames = fileNames.concat(options.typings);
   }
   var program = ts.createProgram(fileNames, compilerOptions, compilerHost);