diff --git a/src/datasources/db/cargobikeAPI.ts b/src/datasources/db/cargobikeAPI.ts
index 71ddab7..40f7093 100644
--- a/src/datasources/db/cargobikeAPI.ts
+++ b/src/datasources/db/cargobikeAPI.ts
@@ -30,6 +30,7 @@ import { EquipmentType } from '../../model/EquipmentType';
 import { BikeEventType } from '../../model/BikeEventType';
 import { Actions } from '../../model/ActionLog';
 import { ResourceLockedError } from '../../errors/ResourceLockedError';
+import { NotFoundError } from '../../errors/NotFoundError';
 
 /**
  * extended datasource to feed resolvers with data about cargoBikes
@@ -82,10 +83,16 @@ export class CargoBikeAPI extends DataSource {
     }
 
     async lockCargoBike (id: number, userId: number) {
+        if (!await this.connection.getRepository(CargoBike).findOne(id)) {
+            throw new NotFoundError('CargoBike', 'id', id);
+        }
         return await LockUtils.lockEntity(this.connection, CargoBike, 'cb', id, userId);
     }
 
     async unlockCargoBike (id: number, userId: number) {
+        if (!await this.connection.getRepository(CargoBike).findOne(id)) {
+            throw new NotFoundError('CargoBike', 'id', id);
+        }
         return await LockUtils.unlockEntity(this.connection, CargoBike, 'cb', id, userId);
     }
 
@@ -115,11 +122,13 @@ export class CargoBikeAPI extends DataSource {
                 .set({ ...cargoBike })
                 .where('id = :id', { id: cargoBike.id })
                 .execute();
+
             equipmentTypeIds && await entityManager.getRepository(CargoBike)
                 .createQueryBuilder('cb')
                 .relation(CargoBike, 'equipmentTypeIds')
                 .of(cargoBike.id)
                 .addAndRemove(equipmentTypeIds, await this.equipmentTypeByCargoBikeId(cargoBike.id));
+
             equipmentIds && await entityManager.getRepository(CargoBike)
                 .createQueryBuilder('cb')
                 .relation(CargoBike, 'equipmentIds')
diff --git a/src/datasources/db/contactinformationAPI.ts b/src/datasources/db/contactinformationAPI.ts
index 5df7bc4..10e7959 100644
--- a/src/datasources/db/contactinformationAPI.ts
+++ b/src/datasources/db/contactinformationAPI.ts
@@ -22,9 +22,9 @@ import { Connection, EntityManager, getConnection } from 'typeorm';
 import { ContactInformation } from '../../model/ContactInformation';
 import { Person } from '../../model/Person';
 import { ActionLogger, DBUtils, LockUtils } from './utils';
-import { GraphQLError } from 'graphql';
 import { LendingStation } from '../../model/LendingStation';
 import { ResourceLockedError } from '../../errors/ResourceLockedError';
+import { NotFoundError } from '../../errors/NotFoundError';
 
 export class ContactInformationAPI extends DataSource {
     connection : Connection
@@ -77,7 +77,11 @@ export class ContactInformationAPI extends DataSource {
                 .update()
                 .set({ ...person })
                 .where('id = :id', { id: person.id })
-                .execute().then(value => { if (value.affected !== 1) { throw new GraphQLError('Id not found'); } });
+                .execute().then(value => {
+                    if (value.affected !== 1) {
+                        throw new NotFoundError('Person', 'id', person.id);
+                    }
+                });
         });
         !keepLock && await this.unlockPerson(person.id, userId);
         return this.personById(person.id);
diff --git a/src/datasources/db/providerAPI.ts b/src/datasources/db/providerAPI.ts
index 9350034..30fabc3 100644
--- a/src/datasources/db/providerAPI.ts
+++ b/src/datasources/db/providerAPI.ts
@@ -25,8 +25,8 @@ import { UserInputError } from 'apollo-server-express';
 import { CargoBike } from '../../model/CargoBike';
 import { LendingStation } from '../../model/LendingStation';
 import { ActionLogger, DBUtils, LockUtils } from './utils';
-import { GraphQLError } from 'graphql';
 import { ResourceLockedError } from '../../errors/ResourceLockedError';
+import { NotFoundError } from '../../errors/NotFoundError';
 
 export class ProviderAPI extends DataSource {
     connection : Connection
@@ -159,7 +159,11 @@ export class ProviderAPI extends DataSource {
                 .update()
                 .set({ ...provider })
                 .where('id = :id', { id: provider.id })
-                .execute().then(value => { if (value.affected !== 1) { throw new GraphQLError('ID not found'); } });
+                .execute().then(value => {
+                    if (value.affected !== 1) {
+                        throw new NotFoundError('Provider', 'id', provider.id);
+                    }
+                });
             await entityManager.getRepository(Provider)
                 .createQueryBuilder('p')
                 .relation(Provider, 'cargoBikeIds')
diff --git a/src/datasources/db/utils.ts b/src/datasources/db/utils.ts
index 6e8b3f9..d377977 100644
--- a/src/datasources/db/utils.ts
+++ b/src/datasources/db/utils.ts
@@ -22,6 +22,7 @@ import { Lockable } from '../../model/CargoBike';
 import { ActionLog, Actions } from '../../model/ActionLog';
 import { UserInputError } from 'apollo-server-express';
 import { ResourceLockedError } from '../../errors/ResourceLockedError';
+import { NotFoundError } from '../../errors/NotFoundError';
 
 export function genDateRange (struct: any) {
     if (!struct.dateRange || !struct.dateRange.from) {
@@ -159,7 +160,7 @@ export class LockUtils {
             .select()
             .where(alias + '.id = :id', { id: id })
             .getOne().catch(() => {
-                throw new UserInputError('ID not found');
+                throw new NotFoundError(target.name, 'id', id);
             });
     }
 
@@ -302,7 +303,7 @@ export class ActionLogger {
             .where('id = :id', { id: updates.id })
             .getRawOne().then(value => {
                 if (value === undefined) {
-                    throw new UserInputError('Id not found');
+                    throw new NotFoundError(target.name, 'id', updates.id);
                 }
                 return value;
             }); // use getRawOne to also get ids of related entities
diff --git a/src/datasources/db/workshopAPI.ts b/src/datasources/db/workshopAPI.ts
index 7c419f3..9c0e510 100644
--- a/src/datasources/db/workshopAPI.ts
+++ b/src/datasources/db/workshopAPI.ts
@@ -22,10 +22,9 @@ import { Connection, EntityManager, getConnection } from 'typeorm';
 import { WorkshopType } from '../../model/WorkshopType';
 import { Workshop } from '../../model/Workshop';
 import { ActionLogger, DBUtils, LockUtils } from './utils';
-import { UserInputError } from 'apollo-server-express';
-import { GraphQLError } from 'graphql';
 import { Participant } from '../../model/Participant';
 import { ResourceLockedError } from '../../errors/ResourceLockedError';
+import { NotFoundError } from '../../errors/NotFoundError';
 
 export class WorkshopAPI extends DataSource {
     connection: Connection
@@ -67,7 +66,11 @@ export class WorkshopAPI extends DataSource {
                 .set({ ...workshop })
                 .where('id = :id', { id: workshop.id })
                 .execute()
-                .then(value => { if (value.affected !== 1) { throw new GraphQLError('ID not found'); } });
+                .then(value => {
+                    if (value.affected !== 1) {
+                        throw new NotFoundError('Workshop', 'id', workshop.id);
+                    }
+                });
         });
         !keepLock && await this.unlockWorkshop(workshop.id, userId);
         return await this.workshopById(workshop.id);
@@ -109,7 +112,11 @@ export class WorkshopAPI extends DataSource {
                 .set({ ...workshopType })
                 .where('id = :id', { id: workshopType.id })
                 .execute()
-                .then(value => { if (value.affected !== 1) { throw new GraphQLError('ID not found'); } });
+                .then(value => {
+                    if (value.affected !== 1) {
+                        throw new NotFoundError('WorkshopType', 'id', workshopType.id);
+                    }
+                });
         });
         !keepLock && await this.unlockWorkshopType(workshopType.id, userId);
         return await this.workshopTypeById(workshopType.id);
diff --git a/src/errors/NotFoundError.ts b/src/errors/NotFoundError.ts
new file mode 100644
index 0000000..d0d1ecf
--- /dev/null
+++ b/src/errors/NotFoundError.ts
@@ -0,0 +1,7 @@
+import { ApolloError } from 'apollo-server-express';
+
+export class NotFoundError extends ApolloError {
+    constructor (type: string, identifierParam: string, identifierValue: any) {
+        super(`${type} with ${identifierParam} = '${identifierValue}' not found.`, 'ENTITY_NOT_FOUND');
+    }
+}