assert imagePath type

sass.js

@@ -70,6 +70,10 @@ var prepareOptions = function (options) {
 
   prepareStats(options, stats);
 
+  if (options.imagePath && typeof options.imagePath !== 'string') {
+    throw new Error('imagePath needs to be a string');
+  }
+
   return {
     file: options.file || null,
     outFile: options.outFile || null,

test/test.js

@@ -135,6 +135,21 @@ describe('compile file with image path', function(){
       }
     });
   });
+  it('should throw on non-string path', function(done) {
+    try {
+      sass.render({
+        file: path.resolve(__dirname, 'image_path.scss'),
+        imagePath: ['/path/to/images'],
+        success: function () {},
+        error: function () {}
+      });
+    } catch(err) {
+      assert(err);
+      return done();
+    }
+
+    done(new Error('did not throw'));
+  });
 });
 
 describe('compile file', function() {