diff --git a/bits/00_header.js b/bits/00_header.js
index 2cd78d2..2829d16 100644
--- a/bits/00_header.js
+++ b/bits/00_header.js
@@ -10,6 +10,7 @@ var PRINTJ/*:PRINTJModule*/ = /*::(*/{}/*:: :any)*/;
 export const version = PRINTJ.version;
 #else
 var PRINTJ/*:PRINTJModule*/;
+#include "05_polyfill.js"
 (function (factory/*:(a:any)=>void*/)/*:void*/ {
 	/*jshint ignore:start */
 	/*eslint-disable */
diff --git a/bits/05_polyfill.js b/bits/05_polyfill.js
new file mode 100644
index 0000000..6275ed3
--- /dev/null
+++ b/bits/05_polyfill.js
@@ -0,0 +1,38 @@
+// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/repeat
+if (!String.prototype.repeat) {
+  String.prototype.repeat = function(count) {
+    'use strict';
+    if (this == null) {
+      throw new TypeError('can\'t convert ' + this + ' to object');
+    }
+    var str = '' + this;
+    count = +count;
+    if (count != count) {
+      count = 0;
+    }
+    if (count < 0) {
+      throw new RangeError('repeat count must be non-negative');
+    }
+    if (count == Infinity) {
+      throw new RangeError('repeat count must be less than infinity');
+    }
+    count = Math.floor(count);
+    if (str.length == 0 || count == 0) {
+      return '';
+    }
+    // Ensuring count is a 31-bit integer allows us to heavily optimize the
+    // main part. But anyway, most current (August 2014) browsers can't handle
+    // strings 1 << 28 chars or longer, so:
+    if (str.length * count >= 1 << 28) {
+      throw new RangeError('repeat count must not overflow maximum string size');
+    }
+    var maxCount = str.length * count;
+    count = Math.floor(Math.log(count) / Math.log(2));
+    while (count) {
+       str += str;
+       count--;
+    }
+    str += str.substring(0, maxCount - str.length);
+    return str;
+  }
+}
diff --git a/bits/40_macros.js b/bits/40_macros.js
index 47b4e92..46811bd 100644
--- a/bits/40_macros.js
+++ b/bits/40_macros.js
@@ -1,12 +1,5 @@
 #define isnan isNaN
-//#define PAD_(x,c) (x >= 0 ? new Array(((x)|0) + 1).join((c)) : "")
-var padstr/*:{[s:string]:string}*/ = {
-	" ": "                                 ",
-	"0": "000000000000000000000000000000000",
-	"7": "777777777777777777777777777777777",
-	"f": "fffffffffffffffffffffffffffffffff"
-};
-#define PAD_(x,c) (x >= 0 ? padstr[c].substr(0,x) : "")
+#define PAD_(x,c) (x >= 0 ? c.repeat(x) : "")
 #ifdef DO_NOT_INLINE
 function pads(x/*:number*/, c/*:string*/)/*:string*/ { return PAD_(x,c); }
 #define PADS(x,c) pads(x,c)
diff --git a/package.json b/package.json
index 381c90d..5bfc17b 100644
--- a/package.json
+++ b/package.json
@@ -13,6 +13,7 @@
 		"printj": "./bin/printj.njs"
 	},
 	"main": "./printj",
+	"module": "./print.mjs",
 	"types": "types",
 	"browser": {
 		"process": false,