diff --git a/pkg/api/handler.go b/pkg/api/handler.go
index d50f5d790..4520343d9 100644
--- a/pkg/api/handler.go
+++ b/pkg/api/handler.go
@@ -156,6 +156,7 @@ func (h Handler) getRouters(rw http.ResponseWriter, request *http.Request) {
 		return
 	}
 
+	rw.Header().Set("Content-Type", "application/json")
 	rw.Header().Set(nextPageHeader, strconv.Itoa(pageInfo.nextPage))
 
 	err = json.NewEncoder(rw).Encode(results[pageInfo.startIndex:pageInfo.endIndex])
@@ -180,6 +181,8 @@ func (h Handler) getRouter(rw http.ResponseWriter, request *http.Request) {
 		Provider:   getProviderName(routerID),
 	}
 
+	rw.Header().Set("Content-Type", "application/json")
+
 	err := json.NewEncoder(rw).Encode(result)
 	if err != nil {
 		log.FromContext(request.Context()).Error(err)
@@ -209,6 +212,7 @@ func (h Handler) getServices(rw http.ResponseWriter, request *http.Request) {
 		return
 	}
 
+	rw.Header().Set("Content-Type", "application/json")
 	rw.Header().Set(nextPageHeader, strconv.Itoa(pageInfo.nextPage))
 
 	err = json.NewEncoder(rw).Encode(results[pageInfo.startIndex:pageInfo.endIndex])
@@ -234,6 +238,8 @@ func (h Handler) getService(rw http.ResponseWriter, request *http.Request) {
 		ServerStatus: service.GetAllStatus(),
 	}
 
+	rw.Header().Add("Content-Type", "application/json")
+
 	err := json.NewEncoder(rw).Encode(result)
 	if err != nil {
 		log.FromContext(request.Context()).Error(err)
@@ -262,6 +268,7 @@ func (h Handler) getMiddlewares(rw http.ResponseWriter, request *http.Request) {
 		return
 	}
 
+	rw.Header().Set("Content-Type", "application/json")
 	rw.Header().Set(nextPageHeader, strconv.Itoa(pageInfo.nextPage))
 
 	err = json.NewEncoder(rw).Encode(results[pageInfo.startIndex:pageInfo.endIndex])
@@ -286,6 +293,8 @@ func (h Handler) getMiddleware(rw http.ResponseWriter, request *http.Request) {
 		Provider:       getProviderName(middlewareID),
 	}
 
+	rw.Header().Set("Content-Type", "application/json")
+
 	err := json.NewEncoder(rw).Encode(result)
 	if err != nil {
 		log.FromContext(request.Context()).Error(err)
@@ -314,6 +323,7 @@ func (h Handler) getTCPRouters(rw http.ResponseWriter, request *http.Request) {
 		return
 	}
 
+	rw.Header().Set("Content-Type", "application/json")
 	rw.Header().Set(nextPageHeader, strconv.Itoa(pageInfo.nextPage))
 
 	err = json.NewEncoder(rw).Encode(results[pageInfo.startIndex:pageInfo.endIndex])
@@ -338,6 +348,8 @@ func (h Handler) getTCPRouter(rw http.ResponseWriter, request *http.Request) {
 		Provider:      getProviderName(routerID),
 	}
 
+	rw.Header().Set("Content-Type", "application/json")
+
 	err := json.NewEncoder(rw).Encode(result)
 	if err != nil {
 		log.FromContext(request.Context()).Error(err)
@@ -366,6 +378,7 @@ func (h Handler) getTCPServices(rw http.ResponseWriter, request *http.Request) {
 		return
 	}
 
+	rw.Header().Set("Content-Type", "application/json")
 	rw.Header().Set(nextPageHeader, strconv.Itoa(pageInfo.nextPage))
 
 	err = json.NewEncoder(rw).Encode(results[pageInfo.startIndex:pageInfo.endIndex])
@@ -390,6 +403,8 @@ func (h Handler) getTCPService(rw http.ResponseWriter, request *http.Request) {
 		Provider:       getProviderName(serviceID),
 	}
 
+	rw.Header().Set("Content-Type", "application/json")
+
 	err := json.NewEncoder(rw).Encode(result)
 	if err != nil {
 		log.FromContext(request.Context()).Error(err)
@@ -414,6 +429,8 @@ func (h Handler) getRuntimeConfiguration(rw http.ResponseWriter, request *http.R
 		TCPServices: h.runtimeConfiguration.TCPServices,
 	}
 
+	rw.Header().Set("Content-Type", "application/json")
+
 	err := json.NewEncoder(rw).Encode(result)
 	if err != nil {
 		log.FromContext(request.Context()).Error(err)
diff --git a/pkg/api/handler_test.go b/pkg/api/handler_test.go
index 2f4b8a98c..6794b977c 100644
--- a/pkg/api/handler_test.go
+++ b/pkg/api/handler_test.go
@@ -326,6 +326,8 @@ func TestHandlerTCP_API(t *testing.T) {
 				return
 			}
 
+			assert.Equal(t, resp.Header.Get("Content-Type"), "application/json")
+
 			contents, err := ioutil.ReadAll(resp.Body)
 			require.NoError(t, err)
 
@@ -869,6 +871,7 @@ func TestHandlerHTTP_API(t *testing.T) {
 				return
 			}
 
+			assert.Equal(t, resp.Header.Get("Content-Type"), "application/json")
 			contents, err := ioutil.ReadAll(resp.Body)
 			require.NoError(t, err)
 
@@ -1022,6 +1025,7 @@ func TestHandler_Configuration(t *testing.T) {
 			require.NoError(t, err)
 
 			assert.Equal(t, test.expected.statusCode, resp.StatusCode)
+			assert.Equal(t, resp.Header.Get("Content-Type"), "application/json")
 
 			contents, err := ioutil.ReadAll(resp.Body)
 			require.NoError(t, err)