diff --git a/src/PhoneNumberFormat.php b/src/PhoneNumberFormat.php
index b1b8da6..cea4033 100644
--- a/src/PhoneNumberFormat.php
+++ b/src/PhoneNumberFormat.php
@@ -17,7 +17,7 @@ class PhoneNumberFormat
      *
      * Example: `+41446681800`.
      */
-    const E164 = 0;
+    public const E164 = 0;
 
     /**
      * The international format.
@@ -27,7 +27,7 @@ class PhoneNumberFormat
      *
      * Example: `+41 44 668 1800`.
      */
-    const INTERNATIONAL = 1;
+    public const INTERNATIONAL = 1;
 
     /**
      * The national format.
@@ -37,7 +37,7 @@ class PhoneNumberFormat
      *
      * Example: `044 668 1800`.
      */
-    const NATIONAL = 2;
+    public const NATIONAL = 2;
 
     /**
      * The RFC 3966 format.
@@ -46,5 +46,5 @@ class PhoneNumberFormat
      *
      * Example: `tel:+41-44-668-1800`.
      */
-    const RFC3966 = 3;
+    public const RFC3966 = 3;
 }
diff --git a/src/PhoneNumberType.php b/src/PhoneNumberType.php
index 44f7615..5db4332 100644
--- a/src/PhoneNumberType.php
+++ b/src/PhoneNumberType.php
@@ -12,12 +12,12 @@ class PhoneNumberType
     /**
      * Fixed line number.
      */
-    const FIXED_LINE = 0;
+    public const FIXED_LINE = 0;
 
     /**
      * Mobile number.
      */
-    const MOBILE = 1;
+    public const MOBILE = 1;
 
     /**
      * Fixed line or mobile number.
@@ -25,17 +25,17 @@ class PhoneNumberType
      * In some regions (e.g. the USA), it is impossible to distinguish between fixed-line and
      * mobile numbers by looking at the phone number itself.
      */
-    const FIXED_LINE_OR_MOBILE = 2;
+    public const FIXED_LINE_OR_MOBILE = 2;
 
     /**
      * Freephone number.
      */
-    const TOLL_FREE = 3;
+    public const TOLL_FREE = 3;
 
     /**
      * Premium rate number.
      */
-    const PREMIUM_RATE = 4;
+    public const PREMIUM_RATE = 4;
 
     /**
      * Shared cost number.
@@ -45,14 +45,14 @@ class PhoneNumberType
      *
      * @see http://en.wikipedia.org/wiki/Shared_Cost_Service
      */
-    const SHARED_COST = 5;
+    public const SHARED_COST = 5;
 
     /**
      * Voice over IP number.
      *
      * This includes TSoIP (Telephony Service over IP).
      */
-    const VOIP = 6;
+    public const VOIP = 6;
 
     /**
      * Personal number.
@@ -62,19 +62,19 @@ class PhoneNumberType
      *
      * @see http://en.wikipedia.org/wiki/Personal_Numbers
      */
-    const PERSONAL_NUMBER = 7;
+    public const PERSONAL_NUMBER = 7;
 
     /**
      * Pager number.
      */
-    const PAGER = 8;
+    public const PAGER = 8;
 
     /**
      * Universal Access Number or Company Number.
      *
      * The number may be further routed to specific offices, but allows one number to be used for a company.
      */
-    const UAN = 9;
+    public const UAN = 9;
 
     /**
      * Unknown number type.
@@ -82,25 +82,25 @@ class PhoneNumberType
      * A phone number is of type UNKNOWN when it does not fit any of the known patterns
      * for a specific region.
      */
-    const UNKNOWN = 10;
+    public const UNKNOWN = 10;
 
     /**
      * Emergency number.
      */
-    const EMERGENCY = 27;
+    public const EMERGENCY = 27;
 
     /**
      * Voicemail number.
      */
-    const VOICEMAIL = 28;
+    public const VOICEMAIL = 28;
 
     /**
      * Short code number.
      */
-    const SHORT_CODE = 29;
+    public const SHORT_CODE = 29;
 
     /**
      * Standard rate number.
      */
-    const STANDARD_RATE = 30;
+    public const STANDARD_RATE = 30;
 }