diff --git a/lib/model.js b/lib/model.js
index 783c0dd40b..6410e6ff8b 100644
--- a/lib/model.js
+++ b/lib/model.js
@@ -4627,9 +4627,10 @@ function _execPopulateQuery(mod, match, select, assignmentOpts, callback) {
       for (const pop of subPopulate) {
         pop._fullPath = basePath + '.' + pop.path;
       }
-    } else if (subPopulate != null) {
+    } else if (subPopulate != null && typeof subPopulate === 'object') {
       subPopulate._fullPath = basePath + '.' + subPopulate.path;
     }
+
     query.populate(subPopulate);
   }
 
diff --git a/test/document.populate.test.js b/test/document.populate.test.js
index 2709e47288..52c76f432d 100644
--- a/test/document.populate.test.js
+++ b/test/document.populate.test.js
@@ -968,6 +968,40 @@ describe('document.populate', function() {
 
     assert.ok(finalDoc.populated('i.g'));
     assert.ok(finalDoc.i.populated('g'));
+  });
+
+  it('works with single strings (gh-11160)', async() => {
+    const bookSchema = mongoose.Schema({
+      title: String,
+      authorId: { type: Schema.ObjectId, ref: 'Author' }
+    });
+
+    const authorSchema = mongoose.Schema({
+      name: String,
+      websiteId: { type: Schema.ObjectId, ref: 'Website' }
+    });
+
+    const websiteSchema = mongoose.Schema({
+      url: String
+    });
+
+    const Book = db.model('Book', bookSchema);
+    const Author = db.model('Author', authorSchema);
+    const Website = db.model('Website', websiteSchema);
+
+
+    const website = new Website({ url: 'http://www.clean-code.com' });
+    const author = new Author({ name: 'Robert C. Martin', websiteId: website._id });
+    const book = new Book({ title: 'Clean Code', authorId: author._id });
+    await Promise.all([
+      website.save(),
+      author.save(),
+      book.save()
+    ]);
 
+    const foundBook = await Book.findOne({ _id: book._id });
+    await foundBook.populate({ path: 'authorId', populate: 'websiteId' });
+    assert.ok(foundBook.populated('authorId'));
+    assert.ok(foundBook.authorId.populated('websiteId'));
   });
 });
diff --git a/test/typescript/main.test.js b/test/typescript/main.test.js
index 2729ef5a0b..e78d9e9d05 100644
--- a/test/typescript/main.test.js
+++ b/test/typescript/main.test.js
@@ -4,44 +4,6 @@ const assert = require('assert');
 const typescript = require('typescript');
 const tsconfig = require('./tsconfig.json');
 
-function printTSErrors(errors) {
-  if (!process.env.D) {
-    return;
-  }
-  if (!errors.length) {
-    return;
-  }
-  errors.forEach(e => {
-    if (typeof e.messageText === 'string') {
-      let lineStart = e.file.text.slice(0, e.start).lastIndexOf('\n');
-      if (lineStart === -1) {
-        lineStart = 0;
-      }
-      let lineEnd = e.file.text.slice(e.start).indexOf('\n');
-      if (lineEnd === -1) {
-        lineEnd = e.file.text.length;
-      } else {
-        lineEnd += e.start;
-      }
-      console.log(`-----\n\nERROR: ${e.messageText}\n\n${e.file.text.slice(lineStart, lineEnd - 1)}\n${' '.repeat(e.start - lineStart - 1)}^`);
-    } else if (e.messageText.messageText) {
-      let lineStart = e.file.text.slice(0, e.start).lastIndexOf('\n');
-      if (lineStart === -1) {
-        lineStart = 0;
-      }
-      let lineEnd = e.file.text.slice(e.start).indexOf('\n');
-      if (lineEnd === -1) {
-        lineEnd = e.file.text.length;
-      } else {
-        lineEnd += e.start;
-      }
-      console.log(`-----\n\nERROR: ${e.messageText.messageText}\n\n${e.file.text.slice(lineStart, lineEnd - 1)}\n${' '.repeat(e.start - lineStart - 1)}^`);
-    } else {
-      console.log(e);
-    }
-  });
-}
-
 describe('typescript syntax', function() {
   this.timeout(60000);
 
@@ -248,4 +210,42 @@ function runTest(file, configOverride) {
   const emitResult = program.emit();
 
   return typescript.getPreEmitDiagnostics(program).concat(emitResult.diagnostics);
+}
+
+function printTSErrors(errors) {
+  if (!process.env.D) {
+    return;
+  }
+  if (!errors.length) {
+    return;
+  }
+  errors.forEach(e => {
+    if (typeof e.messageText === 'string') {
+      let lineStart = e.file.text.slice(0, e.start).lastIndexOf('\n');
+      if (lineStart === -1) {
+        lineStart = 0;
+      }
+      let lineEnd = e.file.text.slice(e.start).indexOf('\n');
+      if (lineEnd === -1) {
+        lineEnd = e.file.text.length;
+      } else {
+        lineEnd += e.start;
+      }
+      console.log(`-----\n\nERROR: ${e.messageText}\n\n${e.file.text.slice(lineStart, lineEnd - 1)}\n${' '.repeat(e.start - lineStart - 1)}^`);
+    } else if (e.messageText.messageText) {
+      let lineStart = e.file.text.slice(0, e.start).lastIndexOf('\n');
+      if (lineStart === -1) {
+        lineStart = 0;
+      }
+      let lineEnd = e.file.text.slice(e.start).indexOf('\n');
+      if (lineEnd === -1) {
+        lineEnd = e.file.text.length;
+      } else {
+        lineEnd += e.start;
+      }
+      console.log(`-----\n\nERROR: ${e.messageText.messageText}\n\n${e.file.text.slice(lineStart, lineEnd - 1)}\n${' '.repeat(e.start - lineStart - 1)}^`);
+    } else {
+      console.log(e);
+    }
+  });
 }
\ No newline at end of file