diff --git a/dddp/api.py b/dddp/api.py
index dfb4c81..cdce7b7 100644
--- a/dddp/api.py
+++ b/dddp/api.py
@@ -11,11 +11,11 @@ import dbarray
 from django.conf import settings
 from django.contrib.auth import get_user_model
 from django.db import connection, connections
-from django.db.models import aggregates, Q, Expression
+from django.db.models import aggregates, Q
 try:
     from django.db.models.expressions import ExpressionNode
 except ImportError:
-    ExpressionNode = None
+    from django.db.models import Expression as ExpressionNode
 from django.db.models.sql import aggregates as sql_aggregates
 from django.utils.encoding import force_text
 from django.db import DatabaseError
@@ -51,6 +51,7 @@ class Array(aggregates.Aggregate):
     """Array aggregate function."""
 
     func = 'ARRAY'
+    function = 'array_agg'
     name = 'Array'
 
     def add_to_query(self, query, alias, col, source, is_summary):
@@ -67,9 +68,17 @@ class Array(aggregates.Aggregate):
                 return 'ArrayType'
 
         new_source = ArrayField()
-        super(Array, self).add_to_query(
-            query, alias, col, new_source, is_summary,
-        )
+        try:
+            super(Array, self).add_to_query(
+                query, alias, col, new_source, is_summary,
+            )
+        except AttributeError:
+            query.aggregates[alias] = new_source
+
+    def convert_value(self, value, expression, connection, context):
+        if not value:
+            return []
+        return value
 
 
 def api_endpoint(path_or_func):
@@ -356,14 +365,11 @@ class Collection(APIMixin):
 
     def serialize(self, obj, meteor_ids):
         """Generate a DDP msg for obj with specified msg type."""
-        if ExpressionNode is None:
-            exps = False
-        else:
-            # check for F expressions
-            exps = [
-                name for name, val in vars(obj).items()
-                if isinstance(val, ExpressionNode)
-            ]
+        # check for F expressions
+        exps = [
+            name for name, val in vars(obj).items()
+            if isinstance(val, ExpressionNode)
+        ]
         if exps:
             # clone/update obj with values but only for the expression fields
             obj = deepcopy(obj)