diff --git a/tests/unit/test_base_formatter.py b/tests/unit/test_base_formatter.py
index dc4a95c..f148806 100644
--- a/tests/unit/test_base_formatter.py
+++ b/tests/unit/test_base_formatter.py
@@ -51,7 +51,15 @@ def test_show_source_returns_nothing_when_not_showing_source():
     formatter = base.BaseFormatter(options(show_source=False))
     assert formatter.show_source(
         style_guide.Error('A000', 'file.py', 1, 1, 'error text', 'line')
-    ) is None
+    ) is ''
+
+
+def test_show_source_returns_nothing_when_there_is_source():
+    """Ensure we return nothing when there is no line."""
+    formatter = base.BaseFormatter(options(show_source=True))
+    assert formatter.show_source(
+        style_guide.Error('A000', 'file.py', 1, 1, 'error text', None)
+    ) is ''
 
 
 @pytest.mark.parametrize('line, column', [