diff --git a/Featurecreep.md b/Featurecreep.md
index c4c394d99..853170f1d 100644
--- a/Featurecreep.md
+++ b/Featurecreep.md
@@ -208,7 +208,7 @@ Teams sind global, d.h. Ein Team kann mehrere Namespaces verwalten.
 
 * [x] Cacher konfigurierbar
 * [ ] Validation der ankommenden structs, am besten mit https://github.com/go-validator/validator
-* [ ] Wenn die ID bei irgendeiner GetByID... Methode < 1 ist soll ein error not exist geworfen werden
+* [x] Wenn die ID bei irgendeiner GetByID... Methode < 1 ist soll ein error not exist geworfen werden
 
 ### Later/Nice to have
 
diff --git a/models/list.go b/models/list.go
index 2e4216409..0572d407e 100644
--- a/models/list.go
+++ b/models/list.go
@@ -30,6 +30,10 @@ func (l *List) AfterLoad() {
 
 // GetListByID returns a list by its ID
 func GetListByID(id int64) (list List, err error) {
+	if id < 1 {
+		return list, ErrListDoesNotExist{ID: id}
+	}
+
 	exists, err := x.ID(id).Get(&list)
 	if err != nil {
 		return list, err
diff --git a/models/list_items.go b/models/list_items.go
index 82ce86ada..699febd3f 100644
--- a/models/list_items.go
+++ b/models/list_items.go
@@ -75,6 +75,10 @@ func GetTasksByListID(listID int64) (tasks []*ListTask, err error) {
 
 // GetListTaskByID returns all tasks a list has
 func GetListTaskByID(listTaskID int64) (listTask ListTask, err error) {
+	if listTaskID < 1 {
+		return ListTask{}, ErrListTaskDoesNotExist{listTaskID}
+	}
+
 	exists, err := x.ID(listTaskID).Get(&listTask)
 	if err != nil {
 		return ListTask{}, err
diff --git a/models/namespace_test.go b/models/namespace_test.go
index 757028450..c324e4beb 100644
--- a/models/namespace_test.go
+++ b/models/namespace_test.go
@@ -40,7 +40,8 @@ func TestNamespace_Create(t *testing.T) {
 
 	// Try inserting one with a nonexistant user
 	nUser := &User{ID: 9482385}
-	err = dummynamespace.Create(nUser)
+	dnsp2 := dummynamespace
+	err = dnsp2.Create(nUser)
 	assert.Error(t, err)
 	assert.True(t, IsErrUserDoesNotExist(err))
 
@@ -88,5 +89,5 @@ func TestNamespace_Create(t *testing.T) {
 	assert.NoError(t, err)
 	assert.Equal(t, reflect.TypeOf(nsps).Kind(), reflect.Slice)
 	s := reflect.ValueOf(nsps)
-	assert.Equal(t, s.Len(), 2)
+	assert.Equal(t, 1, s.Len())
 }
diff --git a/models/namespaces.go b/models/namespaces.go
index f9a7e315b..9355fb972 100644
--- a/models/namespaces.go
+++ b/models/namespaces.go
@@ -28,6 +28,10 @@ func (n *Namespace) AfterLoad() {
 
 // GetNamespaceByID returns a namespace object by its ID
 func GetNamespaceByID(id int64) (namespace Namespace, err error) {
+	if id < 1 {
+		return namespace, ErrNamespaceDoesNotExist{ID: id}
+	}
+
 	namespace.ID = id
 	exists, err := x.Get(&namespace)
 	if err != nil {
diff --git a/models/team_list_test.go b/models/team_list_test.go
index faaecfd74..37effb454 100644
--- a/models/team_list_test.go
+++ b/models/team_list_test.go
@@ -4,7 +4,6 @@ import (
 	"github.com/stretchr/testify/assert"
 	"reflect"
 	"testing"
-	"fmt"
 )
 
 func TestTeamList(t *testing.T) {
@@ -72,7 +71,6 @@ func TestTeamList(t *testing.T) {
 	tl6 := tl
 	tl6.ListID = 3
 	_, err = tl6.ReadAll(&user)
-	fmt.Println(tl6)
 	assert.Error(t, err)
 	assert.True(t, IsErrNeedToHaveListReadAccess(err))
 
diff --git a/models/teams.go b/models/teams.go
index ad4b0f521..d28f62404 100644
--- a/models/teams.go
+++ b/models/teams.go
@@ -62,6 +62,10 @@ type TeamUser struct {
 
 // GetTeamByID gets a team by its ID
 func GetTeamByID(id int64) (team Team, err error) {
+	if id < 1 {
+		return team, ErrTeamDoesNotExist{id}
+	}
+
 	exists, err := x.Where("id = ?", id).Get(&team)
 	if err != nil {
 		return
diff --git a/models/user.go b/models/user.go
index a38ab8ede..f37c1bc09 100644
--- a/models/user.go
+++ b/models/user.go
@@ -48,8 +48,8 @@ func (apiUser *APIUserPassword) APIFormat() User {
 // GetUserByID gets informations about a user by its ID
 func GetUserByID(id int64) (user User, err error) {
 	// Apparently xorm does otherwise look for all users but return only one, which leads to returing one even if the ID is 0
-	if id == 0 {
-		return User{}, nil
+	if id < 1 {
+		return User{}, ErrUserDoesNotExist{}
 	}
 
 	return GetUser(User{ID: id})
diff --git a/models/user_test.go b/models/user_test.go
index 253801fb4..904af48c0 100644
--- a/models/user_test.go
+++ b/models/user_test.go
@@ -67,9 +67,10 @@ func TestCreateUser(t *testing.T) {
 	_, err = GetUserByID(theuser.ID)
 	assert.NoError(t, err)
 
-	// Passing 0 as ID should return an empty user
+	// Passing 0 as ID should return an error
 	_, err = GetUserByID(0)
-	assert.NoError(t, err)
+	assert.Error(t, err)
+	assert.True(t, IsErrUserDoesNotExist(err))
 
 	// Check the user credentials
 	user, err := CheckUserCredentials(&UserLogin{"testuu", "1234"})