diff --git a/src/node/plugin.ts b/src/node/plugin.ts
index c2e43173..65127127 100644
--- a/src/node/plugin.ts
+++ b/src/node/plugin.ts
@@ -118,7 +118,7 @@ export class PluginAPI {
    * loadPlugins loads all plugins based on this.csPlugin,
    * this.csPluginPath and the built in plugins.
    */
-  public async loadPlugins(): Promise<void> {
+  public async loadPlugins(loadBuiltin = true): Promise<void> {
     for (const dir of this.csPlugin.split(":")) {
       if (!dir) {
         continue
@@ -133,8 +133,9 @@ export class PluginAPI {
       await this._loadPlugins(dir)
     }
 
-    // Built-in plugins.
-    await this._loadPlugins(path.join(__dirname, "../../plugins"))
+    if (loadBuiltin) {
+      await this._loadPlugins(path.join(__dirname, "../../plugins"))
+    }
   }
 
   /**
diff --git a/test/plugin.test.ts b/test/plugin.test.ts
index 0c4acb9e..01780eb8 100644
--- a/test/plugin.test.ts
+++ b/test/plugin.test.ts
@@ -15,8 +15,10 @@ describe("plugin", () => {
   let s: httpserver.HttpServer
 
   beforeAll(async () => {
-    papi = new PluginAPI(logger, `${path.resolve(__dirname, "test-plugin")}:meow`)
-    await papi.loadPlugins()
+    // Only include the test plugin to avoid contaminating results with other
+    // plugins that might be on the filesystem.
+    papi = new PluginAPI(logger, `${path.resolve(__dirname, "test-plugin")}:meow`, "")
+    await papi.loadPlugins(false)
 
     const app = express.default()
     papi.mount(app)