diff --git a/src/core/Thing.ts b/src/core/Thing.ts
index af5f9bfe..9680a16f 100644
--- a/src/core/Thing.ts
+++ b/src/core/Thing.ts
@@ -85,7 +85,7 @@ export interface SCThing {
   /**
    * Type of the thing
    */
-  type: string;
+  type: SCThingType;
   /**
    * Universally unique identifier of the thing
    */
diff --git a/src/core/protocol/routes/bulk/BulkRequest.ts b/src/core/protocol/routes/bulk/BulkRequest.ts
index 6e7f1a94..b7aabc60 100644
--- a/src/core/protocol/routes/bulk/BulkRequest.ts
+++ b/src/core/protocol/routes/bulk/BulkRequest.ts
@@ -13,6 +13,7 @@
  * this program. If not, see <https://www.gnu.org/licenses/>.
  */
 import {SCAbstractRoute} from '../../../Route';
+import {SCThingType} from '../../../Thing';
 import {SCISO8601Date} from '../../../types/Time';
 
 /**
@@ -46,9 +47,8 @@ export interface SCBulkParameters {
   /**
    * Type of things that are indexed in this bulk.
    * 
-   * String is an element of the SCThingType enumeration.
    */
-  type: string;
+  type: SCThingType;
 }
 
 /**
diff --git a/src/core/types/config/Backend.ts b/src/core/types/config/Backend.ts
index 67d47f8c..0373e2fd 100644
--- a/src/core/types/config/Backend.ts
+++ b/src/core/types/config/Backend.ts
@@ -12,6 +12,7 @@
  * You should have received a copy of the GNU General Public License along with
  * this program. If not, see <https://www.gnu.org/licenses/>.
  */
+import {SCThingType} from '../../Thing';
 import {SCSearchSortType} from '../sorts/Abstract';
 import {SCUuid} from '../UUID';
 import {SCMonitoringConfiguration} from './Monitoring';
@@ -25,9 +26,8 @@ export interface SCBackendConfiguration {
    *
    * If a type is hidden it won't show in any result unless the type is filtered for
    * 
-   * Strings must be elements of the SCThingType enumeration.
    */
-  hiddenTypes: string[];
+  hiddenTypes: SCThingType[];
 
   /**
    * Name of university
@@ -64,7 +64,7 @@ export interface SCBackendConfigurationSortableField {
    *
    * If no type is given it is assumed it exists on every type
    */
-  onlyOnTypes?: string[];
+  onlyOnTypes?: SCThingType[];
 
   /**
    * A list of supported sorts on this field
@@ -111,7 +111,7 @@ export interface SCBackendConfigurationSearchBoosting {
   /**
    * Type of things the factor should be applied to
    */
-  type: string;
+  type: SCThingType;
 }
 
 /**
@@ -128,7 +128,7 @@ export interface SCBackendAggregationConfiguration {
    *
    * If the type is not given is is assumed the field exists on every type
    */
-  onlyOnTypes?: string[];
+  onlyOnTypes?: SCThingType[];
 }
 
 /**