diff --git a/django/db/models/sql/subqueries.py b/django/db/models/sql/subqueries.py
index 0cd393756d1..f00f1bd68a8 100644
--- a/django/db/models/sql/subqueries.py
+++ b/django/db/models/sql/subqueries.py
@@ -409,7 +409,7 @@ class DateQuery(Query):
         self.select = [select]
         self.select_fields = [None]
         self.select_related = False # See #7097.
-        self.extra = {}
+        self.set_extra_mask([])
         self.distinct = True
         self.order_by = order == 'ASC' and [1] or [-1]
 
diff --git a/tests/regressiontests/queries/models.py b/tests/regressiontests/queries/models.py
index cf21d5210b7..ddac509ede7 100644
--- a/tests/regressiontests/queries/models.py
+++ b/tests/regressiontests/queries/models.py
@@ -755,10 +755,20 @@ Bug #6180, #6203 -- dates with limits and/or counts
 >>> Item.objects.dates('created', 'day')[0]
 datetime.datetime(2007, 12, 19, 0, 0)
 
-Bug #7087 -- dates with extra select columns
+Bug #7087/#12242 -- dates with extra select columns
 >>> Item.objects.dates('created', 'day').extra(select={'a': 1})
 [datetime.datetime(2007, 12, 19, 0, 0), datetime.datetime(2007, 12, 20, 0, 0)]
 
+>>> Item.objects.extra(select={'a': 1}).dates('created', 'day')
+[datetime.datetime(2007, 12, 19, 0, 0), datetime.datetime(2007, 12, 20, 0, 0)]
+
+>>> name="one"
+>>> Item.objects.dates('created', 'day').extra(where=['name=%s'], params=[name])
+[datetime.datetime(2007, 12, 19, 0, 0)]
+
+>>> Item.objects.extra(where=['name=%s'], params=[name]).dates('created', 'day')
+[datetime.datetime(2007, 12, 19, 0, 0)]
+
 Bug #7155 -- nullable dates
 >>> Item.objects.dates('modified', 'day')
 [datetime.datetime(2007, 12, 19, 0, 0)]