diff --git a/web/Dockerfile b/web/Dockerfile
index ca13656c5d..a7b0b0f40e 100644
--- a/web/Dockerfile
+++ b/web/Dockerfile
@@ -68,6 +68,9 @@ ENV REEARTH_PUBLISHED=null
 ENV REEARTH_TITLE=
 ENV REEARTH_UNSAFE_PLUGIN_URLS=[]
 
+RUN --mount=type=cache,target=/var/cache/apk \
+    apk add --no-cache jq
+
 COPY --from=builder --chown=nginx:nginx /app/dist /usr/share/nginx/html
 COPY --chown=nginx:nginx docker/nginx.conf.template /etc/nginx/templates/nginx.conf.template
 COPY --chown=nginx:nginx docker/40-envsubst-on-reearth-config.sh /docker-entrypoint.d
diff --git a/web/docker/40-envsubst-on-reearth-config.sh b/web/docker/40-envsubst-on-reearth-config.sh
index 73ca539de1..41cb51516b 100755
--- a/web/docker/40-envsubst-on-reearth-config.sh
+++ b/web/docker/40-envsubst-on-reearth-config.sh
@@ -36,3 +36,7 @@ wrap_reearth_variables() {
 
 wrap_reearth_variables "$@"
 envsubst < "$_REEARTH_CONFIG_TEMPLATE_FILE" > "$_REEARTH_CONFIG_OUTPUT_FILE"
+if ! jq empty "$_REEARTH_CONFIG_OUTPUT_FILE" > /dev/null 2>&1; then
+  echo "Invalid JSON configuration file $_REEARTH_CONFIG_OUTPUT_FILE" >&2
+  exit 1
+fi