diff --git a/index.js b/index.js
index 7a70a36..d5fe3f0 100644
--- a/index.js
+++ b/index.js
@@ -8,6 +8,8 @@ function parsePhone(e) {
           , d = o = null
           , i = t.getNationalSignificantNumber(r)
           , N = t.getLengthOfNationalDestinationCode(r);
+        var regionForNumber = t.getRegionCodeForNumber(r);
+        null != regionForNumber && (n = regionForNumber);
         N > 0 && (o = i.substring(0, N));
         var d = e.substr(0, e.indexOf(i))
           , a = i.substr((o || "").length)
diff --git a/test.js b/test.js
new file mode 100644
index 0000000..2d369f1
--- /dev/null
+++ b/test.js
@@ -0,0 +1,52 @@
+var assert = require("assert");
+var parsePhone = require("./index.js");
+
+// Regression tests for NANP area codes that were missing from the hand-rolled
+// prefixes table. The bundled libphonenumber's getRegionCodeForNumber() is now
+// used to derive countryISOCode, so these resolve correctly instead of "nothing".
+
+// RED cases: previously returned countryISOCode "nothing".
+assert.strictEqual(parsePhone("17871234567").countryISOCode, "PR",
+    '1787 (Puerto Rico primary area 787) must be "PR"');
+assert.strictEqual(parsePhone("18091234567").countryISOCode, "DO",
+    '1809 (Dominican Republic primary 809) must be "DO"');
+assert.strictEqual(parsePhone("18291234567").countryISOCode, "DO",
+    '1829 (Dominican Republic overlay 829) must be "DO"');
+assert.strictEqual(parsePhone("12681234567").countryISOCode, "AG",
+    '1268 (Antigua & Barbuda 268) must be "AG"');
+
+// Additional NANP area codes that were also missing.
+assert.strictEqual(parsePhone("12841234567").countryISOCode, "VG",
+    '1284 (British Virgin Islands 284) must be "VG"');
+assert.strictEqual(parsePhone("13401234567").countryISOCode, "VI",
+    '1340 (US Virgin Islands 340) must be "VI"');
+assert.strictEqual(parsePhone("16491234567").countryISOCode, "TC",
+    '1649 (Turks & Caicos 649) must be "TC"');
+assert.strictEqual(parsePhone("17841234567").countryISOCode, "VC",
+    '1784 (St Vincent 784) must be "VC"');
+assert.strictEqual(parsePhone("18681234567").countryISOCode, "TT",
+    '1868 (Trinidad & Tobago 868) must be "TT"');
+assert.strictEqual(parsePhone("18691234567").countryISOCode, "KN",
+    '1869 (St Kitts & Nevis 869) must be "KN"');
+
+// Controls: behavior that already worked must be preserved.
+assert.strictEqual(parsePhone("19391234567").countryISOCode, "PR",
+    '1939 (Puerto Rico overlay 939) must remain "PR"');
+assert.strictEqual(parsePhone("18491234567").countryISOCode, "DO",
+    '1849 (Dominican Republic overlay 849) must remain "DO"');
+assert.strictEqual(parsePhone("12025550104").countryISOCode, "US",
+    '1202 (US Washington DC) must remain "US"');
+
+// The result object must be internally consistent: the areaCode that
+// libphonenumber parsed and the countryISOCode must agree (the original
+// self-contradiction had areaCode "787" but countryISOCode "nothing").
+var r787 = parsePhone("17871234567");
+assert.strictEqual(r787.areaCode, "787");
+assert.strictEqual(r787.countryISOCode, "PR");
+
+// Non-NANP number must still resolve (Eswatini country calling code 268).
+var sz = parsePhone("26822171234");
+assert.strictEqual(sz.countryISOCode, "SZ",
+    '+268 (Eswatini) must remain "SZ"');
+
+console.log("All tests passed.");