diff --git a/lib/query.js b/lib/query.js
index 4dfd065f639..cc919b35ade 100644
--- a/lib/query.js
+++ b/lib/query.js
@@ -902,7 +902,6 @@ Query.prototype.select = function select() {
       fields[field] = include;
       userProvidedFields[field] = include;
     }
-
     return this;
   }
 
diff --git a/lib/queryhelpers.js b/lib/queryhelpers.js
index baa548df0e4..f48790615e0 100644
--- a/lib/queryhelpers.js
+++ b/lib/queryhelpers.js
@@ -241,10 +241,9 @@ exports.applyPaths = function applyPaths(fields, schema) {
 
   analyzeSchema(schema);
 
-  let i;
   switch (exclude) {
     case true:
-      for (i = 0; i < excluded.length; ++i) {
+      for (let i = 0; i < excluded.length; ++i) {
         fields[excluded[i]] = 0;
       }
       break;
@@ -255,14 +254,24 @@ exports.applyPaths = function applyPaths(fields, schema) {
           schema.paths['_id'].options.select === false) {
         fields._id = 0;
       }
-      for (i = 0; i < selected.length; ++i) {
+      for (let i = 0; i < selected.length; ++i) {
         fields[selected[i]] = 1;
       }
       break;
     case undefined:
+      if (fields == null) {
+        break;
+      }
+      // Any leftover plus paths must in the schema, so delete them (gh-7017)
+      for (const key of Object.keys(fields || {})) {
+        if (key.charAt(0) === '+') {
+          delete fields[key];
+        }
+      }
+
       // user didn't specify fields, implies returning all fields.
-      // only need to apply excluded fields
-      for (i = 0; i < excluded.length; ++i) {
+      // only need to apply excluded fields and delete any plus paths
+      for (let i = 0; i < excluded.length; ++i) {
         fields[excluded[i]] = 0;
       }
       break;
diff --git a/test/schema.select.test.js b/test/schema.select.test.js
index 12af15fdc73..ca06a4fd077 100644
--- a/test/schema.select.test.js
+++ b/test/schema.select.test.js
@@ -397,16 +397,19 @@ describe('schema select option', function() {
 
       return co(function*() {
         yield db;
-        yield db.db.collection('gh7017').insertOne({
+        yield db.collection('gh7017').insertOne({
           a: 'foo',
           b: 'bar',
           c: 'baz'
         });
 
-        const doc = yield M.find({}, '+c').then(res => res[0]);
+        const q = M.find({}).select('+c');
+        const doc = yield q.then(res => res[0]);
+        assert.deepEqual(q._fields, { a: 0, b: 0 });
+
         assert.strictEqual(doc.a, void 0);
         assert.strictEqual(doc.b, void 0);
-        assert.equal(doc.c, 'baz');
+        assert.equal(doc.toObject().c, 'baz');
       });
     });
   });