diff --git a/CHANGELOG.md b/CHANGELOG.md
index f24a0cc0..873feb86 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -23,6 +23,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Replace traditional syntax array with short syntax array ([#747](https://github.com/jsonrainbow/json-schema/pull/747))
 - Increase phpstan level to 8 with baseline to swallow existing errors ([#673](https://github.com/jsonrainbow/json-schema/pull/673))
 - Add ext-json to composer.json to ensure JSON extension available  ([#759](https://github.com/jsonrainbow/json-schema/pull/759))
+- Add visibility modifiers to class constants ([#757](https://github.com/jsonrainbow/json-schema/pull/757))
 
 ## [6.0.0] - 2024-07-30
 ### Added
diff --git a/src/JsonSchema/ConstraintError.php b/src/JsonSchema/ConstraintError.php
index 52d53211..ac7358a1 100644
--- a/src/JsonSchema/ConstraintError.php
+++ b/src/JsonSchema/ConstraintError.php
@@ -6,51 +6,51 @@
 
 class ConstraintError extends Enum
 {
-    const ADDITIONAL_ITEMS = 'additionalItems';
-    const ADDITIONAL_PROPERTIES = 'additionalProp';
-    const ALL_OF = 'allOf';
-    const ANY_OF = 'anyOf';
-    const DEPENDENCIES = 'dependencies';
-    const DISALLOW = 'disallow';
-    const DIVISIBLE_BY = 'divisibleBy';
-    const ENUM = 'enum';
-    const CONSTANT = 'const';
-    const EXCLUSIVE_MINIMUM = 'exclusiveMinimum';
-    const EXCLUSIVE_MAXIMUM = 'exclusiveMaximum';
-    const FORMAT_COLOR = 'colorFormat';
-    const FORMAT_DATE = 'dateFormat';
-    const FORMAT_DATE_TIME = 'dateTimeFormat';
-    const FORMAT_DATE_UTC = 'dateUtcFormat';
-    const FORMAT_EMAIL = 'emailFormat';
-    const FORMAT_HOSTNAME = 'styleHostName';
-    const FORMAT_IP = 'ipFormat';
-    const FORMAT_PHONE = 'phoneFormat';
-    const FORMAT_REGEX= 'regexFormat';
-    const FORMAT_STYLE = 'styleFormat';
-    const FORMAT_TIME = 'timeFormat';
-    const FORMAT_URL = 'urlFormat';
-    const FORMAT_URL_REF = 'urlRefFormat';
-    const INVALID_SCHEMA = 'invalidSchema';
-    const LENGTH_MAX = 'maxLength';
-    const LENGTH_MIN = 'minLength';
-    const MAXIMUM = 'maximum';
-    const MIN_ITEMS = 'minItems';
-    const MINIMUM = 'minimum';
-    const MISSING_ERROR = 'missingError';
-    const MISSING_MAXIMUM = 'missingMaximum';
-    const MISSING_MINIMUM = 'missingMinimum';
-    const MAX_ITEMS = 'maxItems';
-    const MULTIPLE_OF = 'multipleOf';
-    const NOT = 'not';
-    const ONE_OF = 'oneOf';
-    const REQUIRED = 'required';
-    const REQUIRES = 'requires';
-    const PATTERN = 'pattern';
-    const PREGEX_INVALID = 'pregrex';
-    const PROPERTIES_MIN = 'minProperties';
-    const PROPERTIES_MAX = 'maxProperties';
-    const TYPE = 'type';
-    const UNIQUE_ITEMS = 'uniqueItems';
+    public const ADDITIONAL_ITEMS = 'additionalItems';
+    public const ADDITIONAL_PROPERTIES = 'additionalProp';
+    public const ALL_OF = 'allOf';
+    public const ANY_OF = 'anyOf';
+    public const DEPENDENCIES = 'dependencies';
+    public const DISALLOW = 'disallow';
+    public const DIVISIBLE_BY = 'divisibleBy';
+    public const ENUM = 'enum';
+    public const CONSTANT = 'const';
+    public const EXCLUSIVE_MINIMUM = 'exclusiveMinimum';
+    public const EXCLUSIVE_MAXIMUM = 'exclusiveMaximum';
+    public const FORMAT_COLOR = 'colorFormat';
+    public const FORMAT_DATE = 'dateFormat';
+    public const FORMAT_DATE_TIME = 'dateTimeFormat';
+    public const FORMAT_DATE_UTC = 'dateUtcFormat';
+    public const FORMAT_EMAIL = 'emailFormat';
+    public const FORMAT_HOSTNAME = 'styleHostName';
+    public const FORMAT_IP = 'ipFormat';
+    public const FORMAT_PHONE = 'phoneFormat';
+    public const FORMAT_REGEX= 'regexFormat';
+    public const FORMAT_STYLE = 'styleFormat';
+    public const FORMAT_TIME = 'timeFormat';
+    public const FORMAT_URL = 'urlFormat';
+    public const FORMAT_URL_REF = 'urlRefFormat';
+    public const INVALID_SCHEMA = 'invalidSchema';
+    public const LENGTH_MAX = 'maxLength';
+    public const LENGTH_MIN = 'minLength';
+    public const MAXIMUM = 'maximum';
+    public const MIN_ITEMS = 'minItems';
+    public const MINIMUM = 'minimum';
+    public const MISSING_ERROR = 'missingError';
+    public const MISSING_MAXIMUM = 'missingMaximum';
+    public const MISSING_MINIMUM = 'missingMinimum';
+    public const MAX_ITEMS = 'maxItems';
+    public const MULTIPLE_OF = 'multipleOf';
+    public const NOT = 'not';
+    public const ONE_OF = 'oneOf';
+    public const REQUIRED = 'required';
+    public const REQUIRES = 'requires';
+    public const PATTERN = 'pattern';
+    public const PREGEX_INVALID = 'pregrex';
+    public const PROPERTIES_MIN = 'minProperties';
+    public const PROPERTIES_MAX = 'maxProperties';
+    public const TYPE = 'type';
+    public const UNIQUE_ITEMS = 'uniqueItems';
 
     /**
      * @return string
diff --git a/src/JsonSchema/Constraints/Constraint.php b/src/JsonSchema/Constraints/Constraint.php
index 2390bf90..62da7a85 100644
--- a/src/JsonSchema/Constraints/Constraint.php
+++ b/src/JsonSchema/Constraints/Constraint.php
@@ -21,16 +21,16 @@ abstract class Constraint extends BaseConstraint implements ConstraintInterface
 {
     protected $inlineSchemaProperty = '$schema';
 
-    const CHECK_MODE_NONE =             0x00000000;
-    const CHECK_MODE_NORMAL =           0x00000001;
-    const CHECK_MODE_TYPE_CAST =        0x00000002;
-    const CHECK_MODE_COERCE_TYPES =     0x00000004;
-    const CHECK_MODE_APPLY_DEFAULTS =   0x00000008;
-    const CHECK_MODE_EXCEPTIONS =       0x00000010;
-    const CHECK_MODE_DISABLE_FORMAT =   0x00000020;
-    const CHECK_MODE_EARLY_COERCE =     0x00000040;
-    const CHECK_MODE_ONLY_REQUIRED_DEFAULTS   = 0x00000080;
-    const CHECK_MODE_VALIDATE_SCHEMA =  0x00000100;
+    public const CHECK_MODE_NONE =             0x00000000;
+    public const CHECK_MODE_NORMAL =           0x00000001;
+    public const CHECK_MODE_TYPE_CAST =        0x00000002;
+    public const CHECK_MODE_COERCE_TYPES =     0x00000004;
+    public const CHECK_MODE_APPLY_DEFAULTS =   0x00000008;
+    public const CHECK_MODE_EXCEPTIONS =       0x00000010;
+    public const CHECK_MODE_DISABLE_FORMAT =   0x00000020;
+    public const CHECK_MODE_EARLY_COERCE =     0x00000040;
+    public const CHECK_MODE_ONLY_REQUIRED_DEFAULTS   = 0x00000080;
+    public const CHECK_MODE_VALIDATE_SCHEMA =  0x00000100;
 
     /**
      * Bubble down the path
diff --git a/src/JsonSchema/Constraints/SchemaConstraint.php b/src/JsonSchema/Constraints/SchemaConstraint.php
index b804e6b0..220a2dea 100644
--- a/src/JsonSchema/Constraints/SchemaConstraint.php
+++ b/src/JsonSchema/Constraints/SchemaConstraint.php
@@ -24,7 +24,7 @@
  */
 class SchemaConstraint extends Constraint
 {
-    const DEFAULT_SCHEMA_SPEC = 'http://json-schema.org/draft-04/schema#';
+    private const DEFAULT_SCHEMA_SPEC = 'http://json-schema.org/draft-04/schema#';
 
     /**
      * {@inheritdoc}
diff --git a/src/JsonSchema/Rfc3339.php b/src/JsonSchema/Rfc3339.php
index adca581a..e3226ec7 100644
--- a/src/JsonSchema/Rfc3339.php
+++ b/src/JsonSchema/Rfc3339.php
@@ -4,7 +4,7 @@
 
 class Rfc3339
 {
-    const REGEX = '/^(\d{4}-\d{2}-\d{2}[T ]{1}\d{2}:\d{2}:\d{2})(\.\d+)?(Z|([+-]\d{2}):?(\d{2}))$/';
+    private const REGEX = '/^(\d{4}-\d{2}-\d{2}[T ]{1}\d{2}:\d{2}:\d{2})(\.\d+)?(Z|([+-]\d{2}):?(\d{2}))$/';
 
     /**
      * Try creating a DateTime instance
diff --git a/src/JsonSchema/SchemaStorage.php b/src/JsonSchema/SchemaStorage.php
index 69b8b061..81691699 100644
--- a/src/JsonSchema/SchemaStorage.php
+++ b/src/JsonSchema/SchemaStorage.php
@@ -10,7 +10,7 @@
 
 class SchemaStorage implements SchemaStorageInterface
 {
-    const INTERNAL_PROVIDED_SCHEMA_URI = 'internal://provided-schema/';
+    public const INTERNAL_PROVIDED_SCHEMA_URI = 'internal://provided-schema/';
 
     protected $uriRetriever;
     protected $uriResolver;
diff --git a/src/JsonSchema/Validator.php b/src/JsonSchema/Validator.php
index ac376f9d..97365d43 100644
--- a/src/JsonSchema/Validator.php
+++ b/src/JsonSchema/Validator.php
@@ -22,12 +22,12 @@
  */
 class Validator extends BaseConstraint
 {
-    const SCHEMA_MEDIA_TYPE = 'application/schema+json';
+    public const SCHEMA_MEDIA_TYPE = 'application/schema+json';
 
-    const ERROR_NONE                    = 0x00000000;
-    const ERROR_ALL                     = 0xFFFFFFFF;
-    const ERROR_DOCUMENT_VALIDATION     = 0x00000001;
-    const ERROR_SCHEMA_VALIDATION       = 0x00000002;
+    public const ERROR_NONE                    = 0x00000000;
+    public const ERROR_ALL                     = 0xFFFFFFFF;
+    public const ERROR_DOCUMENT_VALIDATION     = 0x00000001;
+    public const ERROR_SCHEMA_VALIDATION       = 0x00000002;
 
     /**
      * Validates the given data against the schema and returns an object containing the results