diff --git a/addons/web/models/base_document_layout.py b/addons/web/models/base_document_layout.py
index 8d26f61e2f7..6dd2883f3b9 100644
--- a/addons/web/models/base_document_layout.py
+++ b/addons/web/models/base_document_layout.py
@@ -179,9 +179,8 @@ class BaseDocumentLayout(models.TransientModel):
         w = int(50 * base_w / base_h)
         h = 50
 
-        # Converts to RGBA if no alpha detected
-        image_converted = image.convert(
-            'RGBA') if 'A' not in image.getbands() else image
+        # Converts to RGBA (if already RGBA, this is a noop)
+        image_converted = image.convert('RGBA')
         image_resized = image_converted.resize((w, h))
 
         colors = []
diff --git a/addons/web/tests/logo_ci.png b/addons/web/tests/logo_ci.png
new file mode 100644
index 00000000000..1a1ae58e90a
Binary files /dev/null and b/addons/web/tests/logo_ci.png differ
diff --git a/addons/web/tests/test_base_document_layout.py b/addons/web/tests/test_base_document_layout.py
index 55b324117f4..dd8f4e2ad24 100644
--- a/addons/web/tests/test_base_document_layout.py
+++ b/addons/web/tests/test_base_document_layout.py
@@ -194,6 +194,20 @@ class TestBaseDocumentLayout(TestBaseDocumentLayoutHelpers):
             doc_layout.secondary_color = doc_layout.logo_secondary_color
             self.assertColors(doc_layout, self.company_imgs['sweden']['colors'])
 
+    def test_parse_company_colors_grayscale(self):
+        """Grayscale images with transparency"""
+        self.company.write({
+            'primary_color': '#ff0080',
+            'secondary_color': '#00ff00',
+            'paperformat_id': self.env.ref('base.paperformat_us').id,
+        })
+        with Form(self.env['base.document.layout']) as doc_layout:
+            with Image.open(os.path.join(dir_path, 'logo_ci.png'), 'r') as img:
+                base64_img = image_to_base64(img, 'PNG')
+                doc_layout.logo = base64_img
+            self.assertEqual('#8d8d8d', doc_layout.primary_color)
+
+
     # /!\ This case is NOT supported, and probably not supportable
     # res.partner resizes manu-militari the image it is given
     # so res.company._get_logo differs from res.partner.[default image]