diff --git a/.devcontainer/Dockerfile b/.devcontainer/Dockerfile
index 21b36f8c..f5e99919 100644
--- a/.devcontainer/Dockerfile
+++ b/.devcontainer/Dockerfile
@@ -34,6 +34,8 @@ COPY <<EOF /etc/docker/daemon.json
 EOF
 
 RUN curl https://sh.rustup.rs -sSf | sh -s -- -y 
+# nightly build is required for `cargo fmt` as `rustfmt.toml` uses unstable features.
+RUN rustup install nightly
 RUN rustup component add rustfmt
 RUN rustup component add clippy