diff --git a/spec/DatabaseController.spec.js b/spec/DatabaseController.spec.js
index cb8c847700..6583656a23 100644
--- a/spec/DatabaseController.spec.js
+++ b/spec/DatabaseController.spec.js
@@ -434,6 +434,30 @@ describe('DatabaseController', function () {
     });
   });
 
+  describe('reduceInRelation', function () {
+    it('does not throw when a relation constraint operand is null', async () => {
+      const databaseController = new DatabaseController();
+      spyOn(databaseController, 'owningIds').and.returnValue(Promise.resolve([]));
+      const schema = { getExpectedType: () => ({ type: 'Relation' }) };
+
+      await databaseController.reduceInRelation(
+        'Owner',
+        { friends: { $in: [null] } },
+        schema
+      );
+      await databaseController.reduceInRelation(
+        'Owner',
+        { friends: { $nin: [null] } },
+        schema
+      );
+      await databaseController.reduceInRelation(
+        'Owner',
+        { friends: { $ne: null, $in: [] } },
+        schema
+      );
+    });
+  });
+
   describe('reduceOperations', function () {
     const databaseController = new DatabaseController();
 
diff --git a/src/Controllers/DatabaseController.js b/src/Controllers/DatabaseController.js
index 7ddc6e60e4..66262286e2 100644
--- a/src/Controllers/DatabaseController.js
+++ b/src/Controllers/DatabaseController.js
@@ -1130,13 +1130,14 @@ class DatabaseController {
           if (constraintKey === 'objectId') {
             relatedIds = [query[key].objectId];
           } else if (constraintKey == '$in') {
-            relatedIds = query[key]['$in'].map(r => r.objectId);
+            relatedIds = query[key]['$in'].map(r => (r ? r.objectId : undefined));
           } else if (constraintKey == '$nin') {
             isNegation = true;
-            relatedIds = query[key]['$nin'].map(r => r.objectId);
+            relatedIds = query[key]['$nin'].map(r => (r ? r.objectId : undefined));
           } else if (constraintKey == '$ne') {
             isNegation = true;
-            relatedIds = [query[key]['$ne'].objectId];
+            const ne = query[key]['$ne'];
+            relatedIds = [ne ? ne.objectId : undefined];
           } else {
             return;
           }