diff --git a/rest_framework/relations.py b/rest_framework/relations.py
index 1d20ee82b..29585a816 100644
--- a/rest_framework/relations.py
+++ b/rest_framework/relations.py
@@ -109,6 +109,8 @@ class RelatedField(Field):
             try:
                 instance = get_attribute(instance, self.source_attrs[:-1])
 
+                # Handle edge case where the relationship `source` argument
+                # points to a `get_relationship()` method on the model
                 value = instance.serializable_value(self.source_attrs[-1])
                 if is_simple_callable(value):
                     value = value().pk
diff --git a/tests/models.py b/tests/models.py
index 4537ae33e..c265182b7 100644
--- a/tests/models.py
+++ b/tests/models.py
@@ -15,10 +15,7 @@ class RESTFrameworkModel(models.Model):
 
 
 class BasicModel(RESTFrameworkModel):
-    text = models.CharField(
-        max_length=100,
-        verbose_name=_("Text comes here"),
-        help_text=_("Text description."))
+    text = models.CharField(max_length=100, verbose_name=_("Text comes here"), help_text=_("Text description."))
 
 
 class BaseFilterableItem(RESTFrameworkModel):
@@ -48,12 +45,6 @@ class ManyToManySource(RESTFrameworkModel):
 class ForeignKeyTarget(RESTFrameworkModel):
     name = models.CharField(max_length=100)
 
-    def get_first_source(self):
-        try:
-            return self.sources.all()[0]
-        except IndexError:
-            return None
-
 
 class ForeignKeySource(RESTFrameworkModel):
     name = models.CharField(max_length=100)
diff --git a/tests/test_relations_hyperlink.py b/tests/test_relations_hyperlink.py
index cadef5fff..c0642eda2 100644
--- a/tests/test_relations_hyperlink.py
+++ b/tests/test_relations_hyperlink.py
@@ -50,17 +50,6 @@ class ForeignKeyTargetSerializer(serializers.HyperlinkedModelSerializer):
         fields = ('url', 'name', 'sources')
 
 
-class ForeignKeyTargetCallableSourceSerializer(serializers.HyperlinkedModelSerializer):
-    class Meta:
-        model = ForeignKeyTarget
-        fields = ('url', 'name', 'first_source')
-
-    first_source = serializers.HyperlinkedRelatedField(
-        read_only=True,
-        source='get_first_source',
-        view_name='foreignkeysource-detail')
-
-
 class ForeignKeySourceSerializer(serializers.HyperlinkedModelSerializer):
     class Meta:
         model = ForeignKeySource
@@ -455,22 +444,3 @@ class HyperlinkedNullableOneToOneTests(TestCase):
             {'url': 'http://testserver/onetoonetarget/2/', 'name': 'target-2', 'nullable_source': None},
         ]
         self.assertEqual(serializer.data, expected)
-
-
-class HyperlinkedRelationCallableSourceTests(TestCase):
-    urls = 'tests.test_relations_hyperlink'
-
-    def setUp(self):
-        self.target = ForeignKeyTarget.objects.create(name='target-1')
-        ForeignKeySource.objects.create(name='source-1', target=self.target)
-        ForeignKeySource.objects.create(name='source-2', target=self.target)
-
-    def test_relation_field_callable_source(self):
-        serializer = ForeignKeyTargetCallableSourceSerializer(self.target, context={'request': request})
-        expected = {
-            'url': 'http://testserver/foreignkeytarget/1/',
-            'name': 'target-1',
-            'first_source': 'http://testserver/foreignkeysource/1/',
-        }
-        with self.assertNumQueries(1):
-            self.assertEqual(serializer.data, expected)
diff --git a/tests/test_relations_pk.py b/tests/test_relations_pk.py
index 505d4d959..169f7d9c5 100644
--- a/tests/test_relations_pk.py
+++ b/tests/test_relations_pk.py
@@ -30,16 +30,6 @@ class ForeignKeyTargetSerializer(serializers.ModelSerializer):
         fields = ('id', 'name', 'sources')
 
 
-class ForeignKeyTargetCallableSourceSerializer(serializers.ModelSerializer):
-    class Meta:
-        model = ForeignKeyTarget
-        fields = ('id', 'name', 'first_source')
-
-    first_source = serializers.PrimaryKeyRelatedField(
-        read_only=True,
-        source='get_first_source')
-
-
 class ForeignKeySourceSerializer(serializers.ModelSerializer):
     class Meta:
         model = ForeignKeySource
@@ -460,21 +450,3 @@ class PKNullableOneToOneTests(TestCase):
             {'id': 2, 'name': 'target-2', 'nullable_source': 1},
         ]
         self.assertEqual(serializer.data, expected)
-
-
-class PKRelationCallableSourceTests(TestCase):
-
-    def setUp(self):
-        self.target = ForeignKeyTarget.objects.create(name='target-1')
-        self.first_source = ForeignKeySource.objects.create(id=10, name='source-1', target=self.target)
-        ForeignKeySource.objects.create(name='source-2', target=self.target)
-
-    def test_relation_field_callable_source(self):
-        serializer = ForeignKeyTargetCallableSourceSerializer(self.target)
-        expected = {
-            'id': 1,
-            'name': 'target-1',
-            'first_source': 10,
-        }
-        with self.assertNumQueries(1):
-            self.assertEqual(serializer.data, expected)