diff --git a/.travis.yml b/.travis.yml
index f1a3072..a25fbc2 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -9,6 +9,7 @@ env:
 - PACKAGES="django>=1.8,<1.9"
 - PACKAGES="django>=1.10,<1.11"
 - PACKAGES="django>=1.11,<1.12"
+- PACKAGES="django>=2.0,<2.1"
 before_install:
 - pip install codecov
 install:
diff --git a/polymorphic_tree/tests/models.py b/polymorphic_tree/tests/models.py
index 17ea50d..cd4efb5 100644
--- a/polymorphic_tree/tests/models.py
+++ b/polymorphic_tree/tests/models.py
@@ -18,7 +18,8 @@ class PlainC(PlainB):
 
 
 class Model2A(ShowFieldContent, PolymorphicMPTTModel):
-    parent = PolymorphicTreeForeignKey('self', blank=True, null=True, related_name='children', verbose_name='parent')
+    parent = PolymorphicTreeForeignKey('self', blank=True, null=True, related_name='children', verbose_name='parent',
+                                       on_delete=models.CASCADE)
     field1 = models.CharField(max_length=10)
 
 
@@ -35,8 +36,10 @@ class Model2D(Model2C):
 
 
 class One2OneRelatingModel(PolymorphicMPTTModel):
-    parent = PolymorphicTreeForeignKey('self', blank=True, null=True, related_name='children', verbose_name='parent')
-    one2one = models.OneToOneField(Model2A)
+    parent = PolymorphicTreeForeignKey('self', blank=True, null=True, related_name='children', verbose_name='parent',
+                                       on_delete=models.CASCADE)
+    one2one = models.OneToOneField(Model2A,
+                                   on_delete=models.CASCADE)
     field1 = models.CharField(max_length=10)
 
 
@@ -45,7 +48,8 @@ class One2OneRelatingModelDerived(One2OneRelatingModel):
 
 
 class Base(ShowFieldContent, PolymorphicMPTTModel):
-    parent = PolymorphicTreeForeignKey('self', blank=True, null=True, related_name='children', verbose_name='parent')
+    parent = PolymorphicTreeForeignKey('self', blank=True, null=True, related_name='children', verbose_name='parent',
+                                       on_delete=models.CASCADE)
     field_b = models.CharField(max_length=10)
 
 
@@ -71,7 +75,8 @@ class ModelWithCustomParentName(PolymorphicMPTTModel):
                                       blank=True,
                                       null=True,
                                       related_name='subordinate',
-                                      verbose_name='Chief')
+                                      verbose_name='Chief',
+                                      on_delete=models.CASCADE)
     field5 = models.CharField(max_length=10)
 
     class MPTTMeta:
@@ -97,7 +102,8 @@ class ModelWithValidation(PolymorphicMPTTModel):
     parent = PolymorphicTreeForeignKey('self',
                                        blank=True,
                                        null=True,
-                                       related_name='children')
+                                       related_name='children',
+                                       on_delete=models.CASCADE)
 
     field6 = models.CharField(max_length=10)
 
@@ -126,7 +132,8 @@ class ModelWithInvalidMove(PolymorphicMPTTModel):
     parent = PolymorphicTreeForeignKey('self',
                                        blank=True,
                                        null=True,
-                                       related_name='children')
+                                       related_name='children',
+                                       on_delete=models.CASCADE)
 
     field7 = models.CharField(max_length=10)
 
@@ -139,7 +146,8 @@ class ModelMustBeChildRoot(PolymorphicMPTTModel):
     """Model that must be a child"""
     can_be_root = True
 
-    parent = PolymorphicTreeForeignKey('self', blank=True, null=True, related_name='children')
+    parent = PolymorphicTreeForeignKey('self', blank=True, null=True, related_name='children',
+                                       on_delete=models.CASCADE)
     field8 = models.CharField(max_length=10)
 
 
diff --git a/tox.ini b/tox.ini
index 021ae83..0e072f8 100644
--- a/tox.ini
+++ b/tox.ini
@@ -2,8 +2,8 @@
 envlist=
     py27-django{18,110,111},
     py34-django{18,110,111},
-    py35-django{18,110,111},
-    py36-django{111},
+    py35-django{18,110,111,20},
+    py36-django{111,20},
 ;    docs,
 
 [testenv]
@@ -13,6 +13,7 @@ deps =
     django18: Django >= 1.8, < 1.9
     django110: Django >= 1.10, < 1.11
     django111: Django >= 1.11, < 1.12
+    django20:  Django >= 2.0,  <2.1
     py26: mock
     py27: mock
 ;    django-dev: https://github.com/django/django/tarball/master