--- a/release/docker/funsize-update-generator/scripts/funsize.py
+++ b/release/docker/funsize-update-generator/scripts/funsize.py
@@ -225,16 +225,19 @@ def main():
                                option="SourceRepository"),
             "revision": get_option(path, filename="platform.ini",
                                    section="Build", option="SourceStamp"),
             "from_mar": e["from_mar"],
             "to_mar": e["to_mar"],
             "platform": e["platform"],
             "locale": e["locale"],
         }
+        # Override ACCEPTED_MAR_CHANNEL_IDS if needed
+        if "ACCEPTED_MAR_CHANNEL_IDS" in os.environ:
+            mar_data["ACCEPTED_MAR_CHANNEL_IDS"] = os.environ["ACCEPTED_MAR_CHANNEL_IDS"]
         for field in ("update_number", "previousVersion",
                       "previousBuildNumber", "toVersion",
                       "toBuildNumber"):
             if field in e:
                 mar_data[field] = e[field]
         mar_data.update(complete_mars)
         # if branch not set explicitly use repo-name
         mar_data["branch"] = e.get("branch",