diff --git a/.devcontainer/Dockerfile b/.devcontainer/Dockerfile
new file mode 100644
index 0000000..bfdee03
--- /dev/null
+++ b/.devcontainer/Dockerfile
@@ -0,0 +1,8 @@
+FROM mcr.microsoft.com/devcontainers/universal:latest
+
+# Fix: remove legacy Yarn apt repo that can break apt-get update with EXPKEYSIG
+
+RUN rm -f /etc/apt/sources.list.d/yarn.list \
+        /etc/apt/sources.list.d/yarn*.list \
+    && apt-get update \
+    && rm -rf /var/lib/apt/lists/*
diff --git a/.devcontainer/devcontainer.json b/.devcontainer/devcontainer.json
index ec390c2..a0bced6 100644
--- a/.devcontainer/devcontainer.json
+++ b/.devcontainer/devcontainer.json
@@ -2,6 +2,9 @@
     "hostRequirements": {
         "cpus": 8
     },
+    "build": {
+        "dockerfile": "Dockerfile"
+    },
     "customizations": {
         "vscode": {
             "settings": {