diff --git a/backend_client.go b/backend_client.go
index 2e3fb3b..efd5ae1 100644
--- a/backend_client.go
+++ b/backend_client.go
@@ -39,6 +39,9 @@ import (
 var (
 	ErrNotRedirecting         = errors.New("not redirecting to different host")
 	ErrUnsupportedContentType = errors.New("unsupported_content_type")
+
+	ErrIncompleteResponse = errors.New("incomplete OCS response")
+	ErrThrottledResponse  = errors.New("throttled OCS response")
 )
 
 type BackendClient struct {
@@ -193,8 +196,16 @@ func (b *BackendClient) PerformJSONRequest(ctx context.Context, u *url.URL, requ
 			return err
 		} else if ocs.Ocs == nil || ocs.Ocs.Data == nil {
 			log.Printf("Incomplete OCS response %s from %s", string(body), req.URL)
-			return fmt.Errorf("incomplete OCS response")
-		} else if err := json.Unmarshal(*ocs.Ocs.Data, response); err != nil {
+			return ErrIncompleteResponse
+		}
+
+		switch ocs.Ocs.Meta.StatusCode {
+		case http.StatusTooManyRequests:
+			log.Printf("Throttled OCS response %s from %s", string(body), req.URL)
+			return ErrThrottledResponse
+		}
+
+		if err := json.Unmarshal(*ocs.Ocs.Data, response); err != nil {
 			log.Printf("Could not decode OCS response body %s from %s: %s", string(*ocs.Ocs.Data), req.URL, err)
 			return err
 		}
diff --git a/backend_client_test.go b/backend_client_test.go
index 5bae7d5..379bcd0 100644
--- a/backend_client_test.go
+++ b/backend_client_test.go
@@ -30,6 +30,7 @@ import (
 	"net/http/httptest"
 	"net/url"
 	"reflect"
+	"strings"
 	"testing"
 
 	"github.com/dlintw/goconf"
@@ -47,6 +48,14 @@ func returnOCS(t *testing.T, w http.ResponseWriter, body []byte) {
 			Data: (*json.RawMessage)(&body),
 		},
 	}
+	if strings.Contains(t.Name(), "Throttled") {
+		response.Ocs.Meta = OcsMeta{
+			Status:     "failure",
+			StatusCode: 429,
+			Message:    "Reached maximum delay",
+		}
+	}
+
 	data, err := json.Marshal(response)
 	if err != nil {
 		t.Fatal(err)
@@ -206,3 +215,40 @@ func TestPostOnRedirectStatusFound(t *testing.T) {
 		t.Errorf("Expected empty response, got %+v", response)
 	}
 }
+
+func TestHandleThrottled(t *testing.T) {
+	r := mux.NewRouter()
+	r.HandleFunc("/ocs/v2.php/one", func(w http.ResponseWriter, r *http.Request) {
+		returnOCS(t, w, []byte("[]"))
+	})
+	server := httptest.NewServer(r)
+	defer server.Close()
+
+	u, err := url.Parse(server.URL + "/ocs/v2.php/one")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	config := goconf.NewConfigFile()
+	config.AddOption("backend", "allowed", u.Host)
+	config.AddOption("backend", "secret", string(testBackendSecret))
+	if u.Scheme == "http" {
+		config.AddOption("backend", "allowhttp", "true")
+	}
+	client, err := NewBackendClient(config, 1, "0.0", nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	ctx := context.Background()
+	request := map[string]string{
+		"foo": "bar",
+	}
+	var response map[string]string
+	err = client.PerformJSONRequest(ctx, u, request, &response)
+	if err == nil {
+		t.Error("should have triggered an error")
+	} else if !errors.Is(err, ErrThrottledResponse) {
+		t.Error(err)
+	}
+}