diff --git a/rest_framework/fields.py b/rest_framework/fields.py
index fc0c9a444..dd852f3c6 100644
--- a/rest_framework/fields.py
+++ b/rest_framework/fields.py
@@ -1031,8 +1031,8 @@ class DecimalField(Field):
 
         if rounding is not None:
             valid_roundings = [v for k, v in vars(decimal).items() if k.startswith('ROUND_')]
-            assert rounding in valid_roundings, \
-                'Invalid rounding option %s. Valid values for rounding are: %s' % (rounding, valid_roundings)
+            assert rounding in valid_roundings, (
+                'Invalid rounding option %s. Valid values for rounding are: %s' % (rounding, valid_roundings))
         self.rounding = rounding
 
     def to_internal_value(self, data):
diff --git a/tests/test_fields.py b/tests/test_fields.py
index 2f642a77c..8c6360c3b 100644
--- a/tests/test_fields.py
+++ b/tests/test_fields.py
@@ -1092,6 +1092,22 @@ class TestNoDecimalPlaces(FieldValues):
     field = serializers.DecimalField(max_digits=6, decimal_places=None)
 
 
+class TestRoundingDecimalField(TestCase):
+    def test_valid_rounding(self):
+        field = serializers.DecimalField(max_digits=4, decimal_places=2, rounding='ROUND_UP')
+        assert field.to_representation(Decimal('1.234')) == '1.24'
+
+        field = serializers.DecimalField(max_digits=4, decimal_places=2, rounding='ROUND_DOWN')
+        assert field.to_representation(Decimal('1.234')) == '1.23'
+
+    def test_invalid_rounding(self):
+        with pytest.raises(AssertionError) as excinfo:
+            serializers.DecimalField(max_digits=1, decimal_places=1, rounding='ROUND_UNKNOWN')
+        assert 'Invalid rounding option' in str(excinfo.value)
+
+
+
+
 # Date & time serializers...
 
 class TestDateField(FieldValues):