diff --git a/src/Analyser/NodeQueryTrait.php b/src/Analyser/NodeQueryTrait.php
index 76b78f65..59a21298 100644
--- a/src/Analyser/NodeQueryTrait.php
+++ b/src/Analyser/NodeQueryTrait.php
@@ -6,8 +6,9 @@
 
 use function in_array;
 use function rtrim;
-use function str_starts_with;
 use function strcasecmp;
+use function strlen;
+use function strncasecmp;
 
 /**
  * Query helpers shared by {@see ClassNode}, {@see AnonymousClassNode},
@@ -48,10 +49,13 @@ public function dependsOn(string $class, bool $isCaseSensitive = true): bool
 
     public function dependsOnNamespace(string $namespace): bool
     {
-        $prefix = rtrim($namespace, '\\') . '\\';
+        $prefix       = rtrim($namespace, '\\') . '\\';
+        $prefixLength = strlen($prefix);
 
+        // namespace names are case-insensitive; only the prefix is compared,
+        // so a case-sensitive constant name after it is left untouched
         foreach ($this->dependencies as $dependency) {
-            if (str_starts_with($dependency, $prefix)) {
+            if (strncasecmp($dependency, $prefix, $prefixLength) === 0) {
                 return true;
             }
         }
diff --git a/tests/Rule/Usage/MayNotUseNamespaceRuleTest.php b/tests/Rule/Usage/MayNotUseNamespaceRuleTest.php
index 9406b1ec..4539ef74 100644
--- a/tests/Rule/Usage/MayNotUseNamespaceRuleTest.php
+++ b/tests/Rule/Usage/MayNotUseNamespaceRuleTest.php
@@ -100,6 +100,22 @@ public function testViolatesWhenForbiddenNamespaceHasTrailingBackslash(): void
         $this->assertInstanceOf(RuleViolation::class, $mayNotUseNamespaceRule->evaluate($classNode));
     }
 
+    public function testViolatesWhenDepIsInForbiddenNamespaceWithDifferentCase(): void
+    {
+        $mayNotUseNamespaceRule = new MayNotUseNamespaceRule(layer: 'Domain', forbiddenNamespace: 'App');
+        $classNode              = $this->makeNode(['app\\B']);
+
+        $this->assertInstanceOf(RuleViolation::class, $mayNotUseNamespaceRule->evaluate($classNode));
+    }
+
+    public function testPassesWhenDepIsTheForbiddenNamespaceItself(): void
+    {
+        $mayNotUseNamespaceRule = new MayNotUseNamespaceRule(layer: 'Domain', forbiddenNamespace: 'App');
+        $classNode              = $this->makeNode(['App']);
+
+        $this->assertNotInstanceOf(RuleViolation::class, $mayNotUseNamespaceRule->evaluate($classNode));
+    }
+
     public function testPassesWhenDepOnlySharesNamespacePrefix(): void
     {
         $mayNotUseNamespaceRule = new MayNotUseNamespaceRule(layer: 'Domain', forbiddenNamespace: 'Doctrine\\ORM');