diff --git a/addons/web_editor/controllers/main.py b/addons/web_editor/controllers/main.py
index 2203da37d00..f6fabd48ac7 100644
--- a/addons/web_editor/controllers/main.py
+++ b/addons/web_editor/controllers/main.py
@@ -13,6 +13,7 @@ from PIL import Image, ImageFont, ImageDraw
 from lxml import etree
 from base64 import b64decode, b64encode
 from datetime import datetime
+from math import floor
 
 from odoo.http import request, Response
 from odoo import http, tools, _, SUPERUSER_ID
@@ -112,6 +113,13 @@ class Web_Editor(http.Controller):
             bg = bg.replace('rgba', 'rgb')
             bg = ','.join(bg.split(',')[:-1])+')'
 
+        # Convert the opacity value compatible with PIL Image color (0 to 255)
+        # when color specifier is 'rgba'
+        if color is not None and color.startswith('rgba'):
+            *rgb, a = color.strip(')').split(',')
+            opacity = str(floor(float(a) * 255))
+            color = ','.join([*rgb, opacity]) + ')'
+
         # Determine the dimensions of the icon
         image = Image.new("RGBA", (width, height), color)
         draw = ImageDraw.Draw(image)