diff --git a/google-libphonenumber/index.d.ts b/google-libphonenumber/index.d.ts
index 4a0f865373..28f72f67a3 100644
--- a/google-libphonenumber/index.d.ts
+++ b/google-libphonenumber/index.d.ts
@@ -15,11 +15,21 @@ declare namespace libphonenumber {
     interface PhoneNumber {
     }
 
+    export module PhoneNumberUtil {
+        export enum ValidationResult {
+            IS_POSSIBLE,
+            INVALID_COUNTRY_CODE,
+            TOO_SHORT,
+            TOO_LONG
+        }
+    }
+
     export class PhoneNumberUtil {
         static getInstance(): PhoneNumberUtil
         parse(number: string, region: string): PhoneNumber;
         isValidNumber(phoneNumber: PhoneNumber): boolean;
         isPossibleNumber(phoneNumber: PhoneNumber): boolean;
+        isPossibleNumberWithReason(phoneNumber: PhoneNumber): PhoneNumberUtil.ValidationResult;
         isValidNumberForRegion(phoneNumber: PhoneNumber, region: string): boolean;
         getRegionCodeForNumber(phoneNumber: PhoneNumber): string;
         isNANPACountry(regionCode: string): boolean;