diff --git a/src/formatSpecifier.js b/src/formatSpecifier.js
index 8338ec1..ee1567c 100644
--- a/src/formatSpecifier.js
+++ b/src/formatSpecifier.js
@@ -3,10 +3,12 @@ import formatTypes from "./formatTypes";
 // [[fill]align][sign][symbol][0][width][,][.precision][type]
 var re = /^(?:(.)?([<>=^]))?([+\-\( ])?([$#])?(0)?(\d+)?(,)?(\.\d+)?([a-z%])?$/i;
 
-export default function(specifier) {
+export default function formatSpecifier(specifier) {
   return new FormatSpecifier(specifier);
 }
 
+formatSpecifier.prototype = FormatSpecifier.prototype; // instanceof
+
 function FormatSpecifier(specifier) {
   if (!(match = re.exec(specifier))) throw new Error("invalid format: " + specifier);
 
diff --git a/test/formatSpecifier-test.js b/test/formatSpecifier-test.js
index 36cbfca..98672f3 100644
--- a/test/formatSpecifier-test.js
+++ b/test/formatSpecifier-test.js
@@ -8,6 +8,12 @@ tape("formatSpecifier(specifier) throws an error for invalid formats", function(
   test.end();
 });
 
+tape("formatSpecifier(specifier) returns an instanceof formatSpecifier", function(test) {
+  var s = format.formatSpecifier("");
+  test.equal(s instanceof format.formatSpecifier, true);
+  test.end();
+});
+
 tape("formatSpecifier(\"\") has the expected defaults", function(test) {
   var s = format.formatSpecifier("");
   test.equal(s.fill, " ");