diff --git a/src/Collections/CachedConfigCollection.php b/src/Collections/CachedConfigCollection.php
index 4fcfb71..008a7b6 100644
--- a/src/Collections/CachedConfigCollection.php
+++ b/src/Collections/CachedConfigCollection.php
@@ -132,7 +132,7 @@ public function getCollection()
 
         // Load from cache (unless flushing)
         if (!$this->flush) {
-            $this->collection = $this->cache->get(self::CACHE_KEY);
+            $this->collection = $this->cache->get(CachedConfigCollection::CACHE_KEY);
             if ($this->collection) {
                 $this->collectionHash = $this->getHash();
                 return $this->collection;
@@ -154,7 +154,7 @@ public function getCollection()
 
         // Save immediately.
         // Note additional deferred save can occur in _destruct()
-        $this->cache->set(self::CACHE_KEY, $this->collection);
+        $this->cache->set(CachedConfigCollection::CACHE_KEY, $this->collection);
         $this->collectionHash = $this->getHash();
         return $this->collection;
     }
@@ -167,7 +167,7 @@ public function __destruct()
         // Ensure back-end cache is updated
         if ($this->collection && $this->collectionHash) {
             if ($this->getHash() !== $this->collectionHash) {
-                $this->cache->set(self::CACHE_KEY, $this->collection);
+                $this->cache->set(CachedConfigCollection::CACHE_KEY, $this->collection);
             }
 
             // Prevent double-destruct
diff --git a/src/Collections/DeltaConfigCollection.php b/src/Collections/DeltaConfigCollection.php
index 57f1a53..83f8fdb 100644
--- a/src/Collections/DeltaConfigCollection.php
+++ b/src/Collections/DeltaConfigCollection.php
@@ -141,7 +141,7 @@ public function isDeltaReset($class = null)
         return isset($deltas[0]['type'])
             && in_array(
                 $deltas[0]['type'],
-                [self::REPLACE, self::CLEAR]
+                [DeltaConfigCollection::REPLACE, DeltaConfigCollection::CLEAR]
             );
     }
 
@@ -172,12 +172,12 @@ public function set(string $class, ?string $name, mixed $data, array $metadata =
         $this->clearDeltas($class, $name);
         if ($name) {
             $this->addDelta($class, [
-                'type' => self::SET,
+                'type' => DeltaConfigCollection::SET,
                 'config' => [$name => $data],
             ]);
         } else {
             $this->addDelta($class, [
-                'type' => self::REPLACE,
+                'type' => DeltaConfigCollection::REPLACE,
                 'config' => $data,
             ]);
         }
@@ -190,12 +190,12 @@ public function remove(string $class, ?string $name = null): static
         $this->clearDeltas($class, $name);
         if ($name) {
             $this->addDelta($class, [
-                'type' => self::REMOVE,
+                'type' => DeltaConfigCollection::REMOVE,
                 'config' => [$name => true],
             ]);
         } else {
             $this->addDelta($class, [
-                'type' => self::CLEAR,
+                'type' => DeltaConfigCollection::CLEAR,
             ]);
         }
         return $this;
@@ -210,7 +210,7 @@ public function merge(string $class, string|null $name, array $value): static
             $config = $value;
         }
         $this->addDelta($class, [
-            'type' => self::MERGE,
+            'type' => DeltaConfigCollection::MERGE,
             'config' => $config,
         ]);
         return $this;
diff --git a/src/Transformer/YamlTransformer.php b/src/Transformer/YamlTransformer.php
index c8812f9..958e63f 100644
--- a/src/Transformer/YamlTransformer.php
+++ b/src/Transformer/YamlTransformer.php
@@ -333,7 +333,7 @@ protected function calculateDependencies($documents)
             // Add 'after' dependencies
             $dependencies = $this->addDependencies(
                 $header,
-                self::AFTER_FLAG,
+                YamlTransformer::AFTER_FLAG,
                 $dependencies,
                 $documents
             );
@@ -341,7 +341,7 @@ protected function calculateDependencies($documents)
             // Add 'before' dependencies
             $dependencies = $this->addDependencies(
                 $header,
-                self::BEFORE_FLAG,
+                YamlTransformer::BEFORE_FLAG,
                 $dependencies,
                 $documents
             );
@@ -363,7 +363,7 @@ protected function calculateDependencies($documents)
     protected function addDependencies($header, $flag, $dependencies, $documents)
     {
         // If header isn't set then return dependencies
-        if (!isset($header[$flag]) || !in_array($flag, [self::BEFORE_FLAG, self::AFTER_FLAG])) {
+        if (!isset($header[$flag]) || !in_array($flag, [YamlTransformer::BEFORE_FLAG, YamlTransformer::AFTER_FLAG])) {
             return $dependencies;
         }
 
@@ -383,7 +383,7 @@ protected function addDependencies($header, $flag, $dependencies, $documents)
                     $dependencies[$dependencyName] = [];
                 }
 
-                if ($flag == self::AFTER_FLAG) {
+                if ($flag == YamlTransformer::AFTER_FLAG) {
                     // For 'after' we add the given dependency to the current document
                     $dependencies[$header['name']][] = $dependencyName;
                 } else {
@@ -538,12 +538,12 @@ protected function filterByOnlyAndExcept()
         $filtered = [];
         foreach ($documents as $key => $document) {
             // If not all rules match, then we exclude this document
-            if (!$this->testRules($document['header'], self::ONLY_FLAG)) {
+            if (!$this->testRules($document['header'], YamlTransformer::ONLY_FLAG)) {
                 continue;
             }
 
             // If all rules pass, then we exclude this document
-            if ($this->testRules($document['header'], self::EXCEPT_FLAG)) {
+            if ($this->testRules($document['header'], YamlTransformer::EXCEPT_FLAG)) {
                 continue;
             }
 
@@ -566,7 +566,7 @@ protected function testRules($header, $flag)
         // If flag is not set, then it has no tests
         if (!isset($header[$flag])) {
             // We want only to pass, except to fail
-            return $flag === self::ONLY_FLAG;
+            return $flag === YamlTransformer::ONLY_FLAG;
         }
 
         if (!is_array($header[$flag])) {
@@ -592,7 +592,7 @@ protected function testRules($header, $flag)
      * @return bool
      * @throws Exception
      */
-    protected function testSingleRule($rule, $params, $flag = self::ONLY_FLAG)
+    protected function testSingleRule($rule, $params, $flag = YamlTransformer::ONLY_FLAG)
     {
         $rule = strtolower($rule ?? '');
         if (!$this->hasRule($rule)) {
@@ -637,16 +637,16 @@ protected function evaluateConditions($source, $flag, $condition)
             }
 
             // Only fails if any are false
-            if ($flag === self::ONLY_FLAG && !$result) {
+            if ($flag === YamlTransformer::ONLY_FLAG && !$result) {
                 return false;
             }
             // Except succeeds if any true
-            if ($flag === self::EXCEPT_FLAG && $result) {
+            if ($flag === YamlTransformer::EXCEPT_FLAG && $result) {
                 return true;
             }
         }
 
         // Default based on flag
-        return $flag === self::ONLY_FLAG;
+        return $flag === YamlTransformer::ONLY_FLAG;
     }
 }