diff --git a/relational-query.cabal b/relational-query.cabal
--- a/relational-query.cabal
+++ b/relational-query.cabal
@@ -1,5 +1,5 @@
 name:                relational-query
-version:             0.0.1.3
+version:             0.0.1.4
 synopsis:            Typeful, Modular, Relational, algebraic query engine
 description:         This package contiains typeful relation structure and
                      relational-algebraic query building DSL which can
diff --git a/src/Database/Relational/Query/Relation.hs b/src/Database/Relational/Query/Relation.hs
--- a/src/Database/Relational/Query/Relation.hs
+++ b/src/Database/Relational/Query/Relation.hs
@@ -431,7 +431,7 @@
 -- | Scalar subQuery with place-holder parameter 'p'.
 queryScalar' :: (MonadQualify ConfigureQuery m, ScalarDegree r)
              => UniqueRelation p c r
-             -> m (PlaceHolders p, Projection c r)
+             -> m (PlaceHolders p, Projection c (Maybe r))
 queryScalar' ur =
   addPlaceHolders . liftQualify $
   Projection.unsafeFromScalarSubQuery <$> subQueryQualifyFromRelation (unUnique ur)
@@ -439,5 +439,5 @@
 -- | Scalar subQuery.
 queryScalar :: (MonadQualify ConfigureQuery m, ScalarDegree r)
             => UniqueRelation () c r
-            -> m (Projection c r)
+            -> m (Projection c (Maybe r))
 queryScalar =  fmap snd . queryScalar'