diff --git a/package.json b/package.json
index 39bb26c..938a584 100644
--- a/package.json
+++ b/package.json
@@ -34,9 +34,11 @@
   "bugs": {
     "url": "https://github.com/pengx17/monaco-yaml/issues"
   },
+  "optionalDependencies": {
+    "prettier": "^1.19.1"
+  },
   "dependencies": {
     "js-yaml": "^3.12.0",
-    "prettier": "^1.19.1",
     "vscode-json-languageservice": "^3.4.11",
     "vscode-languageserver": "^5.2.1",
     "vscode-uri": "^2.1.1"
@@ -55,6 +57,7 @@
     "monaco-editor-core": "0.15.5",
     "monaco-languages": "1.6.0",
     "monaco-plugin-helpers": "^1.0.2",
+    "prettier": "^1.19.1",
     "requirejs": "^2.3.5",
     "rimraf": "^2.6.2",
     "ts-jest": "^23.10.5",