diff --git a/Dockerfile b/Dockerfile
index 045473f..094f621 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -42,6 +42,5 @@ COPY --from=build /workspace/bin/web-app /usr/local/bin/web-app
 COPY --from=build /workspace/static ./static/
 COPY --from=build /workspace/data ./data/
 
-ENV SERVER_PORT=80
 EXPOSE 80
 ENTRYPOINT ["/usr/local/bin/web-app", "--port 80"]
diff --git a/go-app-compose.yaml b/go-app-compose.yaml
index ec3fab5..8947752 100644
--- a/go-app-compose.yaml
+++ b/go-app-compose.yaml
@@ -8,6 +8,7 @@ services:
     environment:
       - VIRTUAL_HOST=yuanyuanzhou.nl
       - LETSENCRYPT_HOST=yuanyuanzhou.nl
+      - SERVER_PORT=:80
     volumes:
       - db_data:/app/data
     ports:
diff --git a/main.go b/main.go
index d69d93c..7df3154 100644
--- a/main.go
+++ b/main.go
@@ -321,9 +321,9 @@ func splitPDFByPage(inputPath string, outputDir string) error {
 func determinePort() string {
 	port, ok := os.LookupEnv("SERVER_PORT")
 	if !ok {
-		port = ":8080"
+		port = "8080"
 	}
-	return port
+	return ":" + port
 }
 
 func configDatabase() error {