diff --git a/.github/workflows/sub-image-check.yml b/.github/workflows/sub-image-check.yml
index e7a3b53..b29bf20 100644
--- a/.github/workflows/sub-image-check.yml
+++ b/.github/workflows/sub-image-check.yml
@@ -33,6 +33,8 @@ jobs:
         if: github.ref_name == 'main'
         working-directory: .
         run: |
+          apt-get update
+          apt-get install -y libssl-dev pkg-config
           cargo build --release --target x86_64-unknown-linux-gnu
           cargo build --release --target aarch64-unknown-linux-gnu
 
diff --git a/sub-image/src/routes.rs b/sub-image/src/routes.rs
index 04c0116..4672aca 100644
--- a/sub-image/src/routes.rs
+++ b/sub-image/src/routes.rs
@@ -23,7 +23,8 @@ pub async fn root_get() -> Json<RootResponse> {
 pub async fn convert_post(
     body: Json<crate::models::ConvertRequest>,
 ) -> Result<Json<ConvertResponse>> {
-    let backend_host = std::env::var("BACKEND_HOST").unwrap();
+    let backend_host =
+        std::env::var("BACKEND_HOST").unwrap_or_else(|_| "http://localhost:3000".to_string());
     info!("Convert: {:?}", body);
     let base_image = reqwest::get(&if body.url.starts_with('/') {
         format!("{}{}", backend_host, body.url)