diff --git a/Makefile b/Makefile
index 860f8e9d..1ebc3104 100644
--- a/Makefile
+++ b/Makefile
@@ -1,6 +1,5 @@
-NPM ?= $(shell which npm)
 YARN ?= $(shell which yarn)
-PKG_MANAGER ?= $(if $(YARN),$(YARN),$(NPM))
+PKG_MANAGER ?= $(if $(YARN),$(YARN))
 
 .SILENT:
 
diff --git a/package.json b/package.json
index 043e45f4..88ec4891 100644
--- a/package.json
+++ b/package.json
@@ -72,8 +72,8 @@
     "coverage": "node test.js --env=jsdom --coverage --no-cache",
     "test": "node test.js --env=jsdom",
     "build:lib": "babel src/ -d lib/",
-    "build": "npm run build:lib && gulp sass && gulp sass-copy",
-    "prepublish": "npm run build",
+    "build": "yarn run build:lib && gulp sass && gulp sass-copy",
+    "prepublish": "yarn run build",
     "site": "webpack --config webpack.config.site.js && gulp site-sass",
     "lint": "eslint ./*.js src tests website",
     "lint:watch": "esw -w src tests website",