diff --git a/grow/pods/catalog_holder_test.py b/grow/pods/catalog_holder_test.py
index 3fe8f9a6e..cbde10ba6 100644
--- a/grow/pods/catalog_holder_test.py
+++ b/grow/pods/catalog_holder_test.py
@@ -407,6 +407,24 @@ def test_yaml_part_extracted_for_own_locales(self):
             u'Localized yaml doc part in localized doc in unlocalized collection in unlocalized pöd',
             'ja')
 
+    def test_yaml_part_in_unlocalized_doc_extracted_for_own_locales(self):
+        self.assertExtractedFor(
+            self.localized_pod,
+            u'Localized doc part in unlocalized doc in localized collection in localized pöd',
+            'ja')
+        self.assertExtractedFor(
+            self.localized_pod,
+            u'Localized doc part in unlocalized doc in unlocalized collection in localized pöd',
+            'ja')
+        self.assertExtractedFor(
+            self.unlocalized_pod,
+            u'Localized doc part in unlocalized doc in localized collection in unlocalized pöd',
+            'ja')
+        self.assertExtractedFor(
+            self.unlocalized_pod,
+            u'Localized doc part in unlocalized doc in unlocalized collection in unlocalized pöd',
+            'ja')
+
     def test_multilocale_yaml_part_extracted_for_own_locales(self):
         self.assertExtractedFor(
             self.localized_pod,
@@ -452,18 +470,34 @@ def test_yaml_doc_extracted_for_collection_locales(self):
             self.unlocalized_pod,
             u'Unlocalized yaml doc in localized collection in unlocalized pöd',
             'fr')
+        self.assertExtractedFor(
+            self.localized_pod,
+            u'Unlocalized base doc part in localized collection in localized pöd',
+            'fr')
+        self.assertExtractedFor(
+            self.unlocalized_pod,
+            u'Unlocalized base doc part in localized collection in unlocalized pöd',
+            'fr')
 
     def test_yaml_doc_extracted_for_podspec_locales(self):
         self.assertExtractedFor(
             self.localized_pod,
             u'Unlocalized yaml doc in unlocalized collection in localized pöd',
             'de')
+        self.assertExtractedFor(
+            self.localized_pod,
+            u'Unlocalized base doc part in unlocalized collection in localized pöd',
+            'de')
 
     def test_yaml_doc_extracted_for_no_locales(self):
         self.assertExtractedFor(
             self.unlocalized_pod,
             u'Unlocalized yaml doc in unlocalized collection in unlocalized pöd',
             [])
+        self.assertExtractedFor(
+            self.localized_pod,
+            u'Unlocalized base doc part in unlocalized collection in unlocalized pöd',
+            'de')
 
     # ------------------------------------------------
     # YAML files in /content/ root
diff --git a/grow/pods/formats.py b/grow/pods/formats.py
index 6a32e48c1..ba97c0eff 100644
--- a/grow/pods/formats.py
+++ b/grow/pods/formats.py
@@ -94,7 +94,7 @@ def _validate_non_base_part(self, fields):
         # Any additional parts after base part MUST declare one or more locales
         # (otherwise there's no point)
         if '$locale' not in fields and '$locales' not in fields:
-            text = 'You must specify either $locale or $locales.'
+            text = 'You must specify either $locale or $locales for each document part.'
             raise BadFormatError(text)
         self._validate_fields(fields)
 
diff --git a/grow/testing/testdata/extract_localized/localized_pod/content/localized_collection/unlocalized_doc_with_localized_parts.yaml b/grow/testing/testdata/extract_localized/localized_pod/content/localized_collection/unlocalized_doc_with_localized_parts.yaml
new file mode 100644
index 000000000..82ecc5edf
--- /dev/null
+++ b/grow/testing/testdata/extract_localized/localized_pod/content/localized_collection/unlocalized_doc_with_localized_parts.yaml
@@ -0,0 +1,5 @@
+---
+foo@: Unlocalized base doc part in localized collection in localized pöd
+---
+$locale: ja
+foo@: Localized doc part in unlocalized doc in localized collection in localized pöd
diff --git a/grow/testing/testdata/extract_localized/localized_pod/content/unlocalized_collection/unlocalized_doc_with_localized_parts.yaml b/grow/testing/testdata/extract_localized/localized_pod/content/unlocalized_collection/unlocalized_doc_with_localized_parts.yaml
new file mode 100644
index 000000000..ed5acba5e
--- /dev/null
+++ b/grow/testing/testdata/extract_localized/localized_pod/content/unlocalized_collection/unlocalized_doc_with_localized_parts.yaml
@@ -0,0 +1,5 @@
+---
+foo@: Unlocalized base doc part in unlocalized collection in localized pöd
+---
+$locale: ja
+foo@: Localized doc part in unlocalized doc in unlocalized collection in localized pöd
diff --git a/grow/testing/testdata/extract_localized/unlocalized_pod/content/localized_collection/unlocalized_doc_with_localized_parts.yaml b/grow/testing/testdata/extract_localized/unlocalized_pod/content/localized_collection/unlocalized_doc_with_localized_parts.yaml
new file mode 100644
index 000000000..4c733114c
--- /dev/null
+++ b/grow/testing/testdata/extract_localized/unlocalized_pod/content/localized_collection/unlocalized_doc_with_localized_parts.yaml
@@ -0,0 +1,5 @@
+---
+foo@: Unlocalized base doc part in localized collection in unlocalized pöd
+---
+$locale: ja
+foo@: Localized doc part in unlocalized doc in localized collection in unlocalized pöd
diff --git a/grow/testing/testdata/extract_localized/unlocalized_pod/content/unlocalized_collection/unlocalized_doc_with_localized_parts.yaml b/grow/testing/testdata/extract_localized/unlocalized_pod/content/unlocalized_collection/unlocalized_doc_with_localized_parts.yaml
new file mode 100644
index 000000000..171bc860e
--- /dev/null
+++ b/grow/testing/testdata/extract_localized/unlocalized_pod/content/unlocalized_collection/unlocalized_doc_with_localized_parts.yaml
@@ -0,0 +1,5 @@
+---
+foo@: Unlocalized base doc part in unlocalized collection in unlocalized pöd
+---
+$locale: ja
+foo@: Localized doc part in unlocalized doc in unlocalized collection in unlocalized pöd