diff --git a/backend/services/controller/internal/api/api.go b/backend/services/controller/internal/api/api.go
index dcecc77..5d4635d 100644
--- a/backend/services/controller/internal/api/api.go
+++ b/backend/services/controller/internal/api/api.go
@@ -3,6 +3,7 @@ package api
 import (
 	"encoding/json"
 	"github.com/gorilla/mux"
+	"github.com/leandrofars/oktopus/internal/api/middleware"
 	"github.com/leandrofars/oktopus/internal/db"
 	"github.com/leandrofars/oktopus/internal/mtp"
 	usp_msg "github.com/leandrofars/oktopus/internal/usp_message"
@@ -45,6 +46,10 @@ func StartApi(a Api) {
 	r.HandleFunc("/device/{sn}/del", a.deviceDeleteMsg).Methods("PUT")
 	r.HandleFunc("/device/{sn}/set", a.deviceUpdateMsg).Methods("PUT")
 
+	r.Use(func(handler http.Handler) http.Handler {
+		return middleware.Middleware(handler)
+	})
+
 	srv := &http.Server{
 		Addr: "0.0.0.0:" + a.Port,
 		// Good practice to set timeouts to avoid Slowloris attacks.
diff --git a/backend/services/controller/internal/api/middleware/middleware.go b/backend/services/controller/internal/api/middleware/middleware.go
new file mode 100644
index 0000000..97edbe4
--- /dev/null
+++ b/backend/services/controller/internal/api/middleware/middleware.go
@@ -0,0 +1,12 @@
+package middleware
+
+import "net/http"
+
+func Middleware(next http.Handler) http.Handler {
+	return http.HandlerFunc(
+		func(w http.ResponseWriter, r *http.Request) {
+			w.Header().Set("Content-Type", "application/json")
+			next.ServeHTTP(w, r)
+		},
+	)
+}