diff --git a/src/common/load-plugins.js b/src/common/load-plugins.js
index 604215a2b..8036b989a 100644
--- a/src/common/load-plugins.js
+++ b/src/common/load-plugins.js
@@ -7,6 +7,7 @@ const path = require("path");
 const resolve = require("resolve");
 const thirdParty = require("./third-party");
 const internalPlugins = require("./internal-plugins");
+const partition = require("../utils/partition");
 
 function loadPlugins(plugins, pluginSearchDirs) {
   if (!plugins) {
@@ -24,7 +25,12 @@ function loadPlugins(plugins, pluginSearchDirs) {
     }
   }
 
-  const externalManualLoadPluginInfos = plugins.map(pluginName => {
+  const [externalPluginNames, externalPluginInstances] = partition(
+    plugins,
+    plugin => typeof plugin === "string"
+  );
+
+  const externalManualLoadPluginInfos = externalPluginNames.map(pluginName => {
     let requirePath;
     try {
       // try local files
@@ -69,12 +75,14 @@ function loadPlugins(plugins, pluginSearchDirs) {
   const externalPlugins = uniqBy(
     externalManualLoadPluginInfos.concat(externalAutoLoadPluginInfos),
     "requirePath"
-  ).map(externalPluginInfo =>
-    Object.assign(
-      { name: externalPluginInfo.name },
-      eval("require")(externalPluginInfo.requirePath)
+  )
+    .map(externalPluginInfo =>
+      Object.assign(
+        { name: externalPluginInfo.name },
+        eval("require")(externalPluginInfo.requirePath)
+      )
     )
-  );
+    .concat(externalPluginInstances);
 
   return internalPlugins.concat(externalPlugins);
 }
diff --git a/src/utils/partition.js b/src/utils/partition.js
new file mode 100644
index 000000000..979a6ef5e
--- /dev/null
+++ b/src/utils/partition.js
@@ -0,0 +1,14 @@
+"use strict";
+
+module.exports = function partition(array, fn) {
+  const a = [];
+  const b = [];
+  array.forEach(item => {
+    if (fn(item)) {
+      a.push(item);
+    } else {
+      b.push(item);
+    }
+  });
+  return [a, b];
+};
diff --git a/tests_integration/__tests__/__snapshots__/format.js.snap b/tests_integration/__tests__/__snapshots__/format.js.snap
index e25b72a35..405a972b8 100644
--- a/tests_integration/__tests__/__snapshots__/format.js.snap
+++ b/tests_integration/__tests__/__snapshots__/format.js.snap
@@ -4,6 +4,8 @@ exports[`html parser should handle CRLF correctly 1`] = `"\\"<!--\\\\r\\\\n  tes
 
 exports[`markdown parser should handle CRLF correctly 1`] = `"\\"\`\`\`\\\\r\\\\n\\\\r\\\\n\\\\r\\\\n\`\`\`\\\\r\\\\n\\""`;
 
+exports[`should work with foo plugin instance 1`] = `"\\"tabWidth:8\\""`;
+
 exports[`typescript parser should throw the first error when both JSX and non-JSX mode failed 1`] = `
 "Expression expected. (9:7)
    7 | );
diff --git a/tests_integration/__tests__/format.js b/tests_integration/__tests__/format.js
index bf4d30ff6..e7067593e 100644
--- a/tests_integration/__tests__/format.js
+++ b/tests_integration/__tests__/format.js
@@ -1,6 +1,7 @@
 "use strict";
 
 const prettier = require("prettier/local");
+const fooPlugin = require("../plugins/defaultOptions/plugin");
 
 test("yaml parser should handle CRLF correctly", () => {
   const input = "a:\r\n  123\r\n";
@@ -41,3 +42,12 @@ test("markdown parser should handle CRLF correctly", () => {
     JSON.stringify(prettier.format(input, { parser: "markdown" }))
   ).toMatchSnapshot();
 });
+
+test("should work with foo plugin instance", () => {
+  const input = "a:\r\n  123\r\n";
+  expect(
+    JSON.stringify(
+      prettier.format(input, { parser: "foo-parser", plugins: [fooPlugin] })
+    )
+  ).toMatchInlineSnapshot(`"\\"tabWidth:8\\""`);
+});