diff --git a/thumbor/engines/pil.py b/thumbor/engines/pil.py
index <HASH>..<HASH> 100644
--- a/thumbor/engines/pil.py
+++ b/thumbor/engines/pil.py
@@ -116,6 +116,11 @@ class Engine(BaseEngine):
             if quality is None:
                 options['quality'] = 'keep'
 
+            if self.image.mode == 'L':
+                self.image = self.image.convert('RGB')
+                if quality is None:
+                    options['quality'] = None
+
         if options['quality'] is None:
             options['quality'] = self.context.config.QUALITY
 
diff --git a/vows/handler_images_vows.py b/vows/handler_images_vows.py
index <HASH>..<HASH> 100644
--- a/vows/handler_images_vows.py
+++ b/vows/handler_images_vows.py
@@ -294,3 +294,12 @@ class GetImageWithAutoWebP(BaseContext):
         def should_be_200(self, response):
             code, _ = response
             expect(code).to_equal(200)
+
+    class WithMonochromaticJPEG(BaseContext):
+        def topic(self):
+            response = self.get('/unsafe/wellsford.jpg')
+            return (response.code, response.headers)
+
+        def should_be_200(self, response):
+            code, _ = response
+            expect(code).to_equal(200)
Fix #<I>.

Monochromatic JPG images were being handled incorrectly. Now it works as
expected.