diff --git a/src/PIL/WebPImagePlugin.py b/src/PIL/WebPImagePlugin.py
index e53885edb25..1c38c4a4162 100644
--- a/src/PIL/WebPImagePlugin.py
+++ b/src/PIL/WebPImagePlugin.py
@@ -369,6 +369,7 @@ def _supported_modes():
         "F",
         "P",
         "LA",
+        "LAB",
         "L",
         "1",
     ]