diff --git a/formulation/templatetags/formulation.py b/formulation/templatetags/formulation.py
index 06bf728..3d81f6f 100644
--- a/formulation/templatetags/formulation.py
+++ b/formulation/templatetags/formulation.py
@@ -118,7 +118,14 @@ def render(self, context):
 @register.simple_tag(takes_context=True)
 def field(context, field, widget=None, **kwargs):
     if isinstance(field, six.string_types):
-        field = context['formulation-form'][field]
+        formulation_form = context['formulation-form']
+        if formulation_form is None:
+            raise ValueError(
+                'The form field you\'re trying to access probably doesn\'t '
+                'exist on the form.'
+            )
+        else:
+            field = formulation_form[field]
 
     field_data = {
         'form_field': field,
diff --git a/tests/tests/test_tags.py b/tests/tests/test_tags.py
index e533465..82fbfce 100644
--- a/tests/tests/test_tags.py
+++ b/tests/tests/test_tags.py
@@ -99,6 +99,7 @@ class FieldTagTest(TemplateTestMixin, SimpleTestCase):
     PARTIALS = {
         'use_correct_block': "{% field form.name 'custom_input' %}",
         'unknown_block': "{% field form.name 'does_not_exist' %}",
+        'unknown_field': "{% field form.choose_unicorn 'TextInput' %}",
         'auto_widget1': "{% field form.name %}",
         'auto_widget2': "{% field form.gender %}",
         'auto_widget3': "{% field form.is_cool %}",
@@ -124,6 +125,19 @@ def test_unknown_block(self):
         with self.assertRaises(TemplateSyntaxError):
             template.render(self.context)
 
+    def test_wrong_field(self):
+        """
+        Tests the debug information when trying to render a non-existent field.
+        """
+        template = get_template('unknown_field')
+        with self.assertRaises(ValueError) as exc:
+            template.render(self.context)
+        self.assertEqual(
+            exc.exception.args[0],
+            'The form field you\'re trying to access probably doesn\'t '
+            'exist on the form.'
+        )
+
     def test_auto_widget(self):
         """
         Choose the correct widget according to the form field.