diff --git a/README.md b/README.md
index ec0d59f1..59cd76d6 100644
--- a/README.md
+++ b/README.md
@@ -287,6 +287,7 @@ If you're building a custom branch, or want to use the develop branch, check out
 riot-web branch and then run:
 ```bash
 docker build -t vectorim/riot-web:develop \
+    --build-arg USE_CUSTOM_SDKS=true \
     --build-arg REACT_SDK_REPO="https://github.com/matrix-org/matrix-react-sdk.git" \
     --build-arg REACT_SDK_BRANCH="develop" \
     --build-arg JS_SDK_REPO="https://github.com/matrix-org/matrix-js-sdk.git" \