diff --git a/lib/minify.js b/lib/minify.js
index a68cbf3a..8760be13 100644
--- a/lib/minify.js
+++ b/lib/minify.js
@@ -1,10 +1,24 @@
 "use strict";
 
 var to_ascii = typeof atob == "undefined" ? function(b64) {
-    return new Buffer(b64, "base64").toString();
+    if (Buffer.from && Buffer.from !== Uint8Array.from) {
+      // Node >= 4.5.0
+      return Buffer.from(b64, "base64").toString();
+    } else {
+      // Node < 4.5.0, old API, manual safeguards
+      if (typeof b64 !== "string") throw new Errror("\"b64\" must be a string");
+      return new Buffer(b64, "base64").toString();
+    }
 } : atob;
 var to_base64 = typeof btoa == "undefined" ? function(str) {
-    return new Buffer(str).toString("base64");
+    if (Buffer.from && Buffer.from !== Uint8Array.from) {
+      // Node >= 4.5.0
+      return Buffer.from(str, "ascii").toString("base64");
+    } else {
+      // Node < 4.5.0, old API, manual safeguards
+      if (typeof str !== "string") throw new Errror("\"str\" must be a string");
+      return new Buffer(str).toString("base64");
+    }
 } : btoa;
 
 function read_source_map(code) {