diff --git a/packages/docusaurus/src/server/configValidation.ts b/packages/docusaurus/src/server/configValidation.ts
index 52fbb08a3d..0e8700ac9f 100644
--- a/packages/docusaurus/src/server/configValidation.ts
+++ b/packages/docusaurus/src/server/configValidation.ts
@@ -42,6 +42,7 @@ export const DEFAULT_CONFIG: Pick<
 const PluginSchema = Joi.alternatives().try(
   Joi.string(),
   Joi.array().items(Joi.string().required(), Joi.object().required()).length(2),
+  Joi.bool().equal(false), // In case of conditional adding of plugins.
 );
 
 const ThemeSchema = Joi.alternatives().try(