diff --git a/packages/size-limit/load-plugins.js b/packages/size-limit/load-plugins.js
index 11c156ef..d8e779cc 100644
--- a/packages/size-limit/load-plugins.js
+++ b/packages/size-limit/load-plugins.js
@@ -18,6 +18,7 @@ module.exports = function loadPlugins(pkg) {
 
   let list = toArray(pkg.packageJson.dependencies)
     .concat(toArray(pkg.packageJson.devDependencies))
+    .concat(toArray(pkg.packageJson.optionalDependencies))
     .filter(i => i.startsWith('@size-limit/'))
     .reduce(
       (all, i) =>