diff --git a/README.md b/README.md
index f172f4a..f47633e 100644
--- a/README.md
+++ b/README.md
@@ -75,7 +75,7 @@ return static function (RectorConfig $rectorConfig): void {
 };
 ```
 
-`ALLOW_NAMED_VARIADIC_ARGUMENTS` is enabled by default. If you set it to `false`, calls that include variadic arguments are skipped.
+`ALLOW_NAMED_VARIADIC_ARGUMENTS` is enabled by default. For user-defined callables, the rule may still synthesize names for variadic entries (for example `values1`, `values2`), because PHP accepts unknown named arguments there and forwards them into the variadic parameter. Internal/native variadic callables such as `sprintf()` are skipped when a variadic tail is actually passed, because PHP rejects unknown named parameters there and named arguments also cannot be followed by positional ones. If you set it to `false`, calls that include variadic arguments are skipped entirely.
 
 #### Implementing Your Own Strategy
 
diff --git a/src/AddNamedArgumentsRector.php b/src/AddNamedArgumentsRector.php
index 8cedcda..553eae8 100644
--- a/src/AddNamedArgumentsRector.php
+++ b/src/AddNamedArgumentsRector.php
@@ -103,11 +103,20 @@ public function refactor(Node $node): ?Node
             return null;
         }
 
-        if (! $this->allowNamedVariadicArguments && $this->hasVariadicArguments($node, $parameters)) {
+        $hasVariadicArguments = $this->hasVariadicArguments($node, $parameters);
+        if (! $this->allowNamedVariadicArguments && $hasVariadicArguments) {
             return null;
         }
 
-        $hasChanges = $this->addNamesToArgs(node: $node, parameters: $parameters);
+        $functionReflection = Reflection::getFunctionReflection(node: $node, classReflection: $classReflection);
+        if ($hasVariadicArguments && ($functionReflection?->isInternal() ?? false)) {
+            return null;
+        }
+
+        $hasChanges = $this->addNamesToArgs(
+            node: $node,
+            parameters: $parameters,
+        );
 
         if (! $hasChanges) {
             return null;
@@ -152,9 +161,13 @@ private function addNamesToArgs(
                 $variadicArgCounters[$variadicParameterName] = $variadicIndex;
 
                 $arg->name = new Identifier(name: $variadicParameterName . $variadicIndex);
-            } else {
-                $arg->name = new Identifier(name: $parameter->getName());
+                $namedArgs[] = $arg;
+                $hasChanges = true;
+
+                continue;
             }
+
+            $arg->name = new Identifier(name: $parameter->getName());
             $namedArgs[] = $arg;
             $hasChanges = true;
         }
diff --git a/tests/DefaultStrategy/Fixture/internal_variadic.php.inc b/tests/DefaultStrategy/Fixture/internal_variadic.php.inc
new file mode 100644
index 0000000..cb79daf
--- /dev/null
+++ b/tests/DefaultStrategy/Fixture/internal_variadic.php.inc
@@ -0,0 +1,11 @@
+<?php
+
+array_merge(['a' => 1], ['b' => 2], ['c' => 3]);
+
+?>
+-----
+<?php
+
+array_merge(['a' => 1], ['b' => 2], ['c' => 3]);
+
+?>
diff --git a/tests/DefaultStrategy/Fixture/userland_variadic_function.php.inc b/tests/DefaultStrategy/Fixture/userland_variadic_function.php.inc
new file mode 100644
index 0000000..af98583
--- /dev/null
+++ b/tests/DefaultStrategy/Fixture/userland_variadic_function.php.inc
@@ -0,0 +1,11 @@
+<?php
+
+userlandVariadicFoo('php', '--version', '--ansi');
+
+?>
+-----
+<?php
+
+userlandVariadicFoo(command: 'php', values1: '--version', values2: '--ansi');
+
+?>
diff --git a/tests/DefaultStrategy/Fixture/variadic.php.inc b/tests/DefaultStrategy/Fixture/variadic.php.inc
index eaf24e1..ef468d2 100644
--- a/tests/DefaultStrategy/Fixture/variadic.php.inc
+++ b/tests/DefaultStrategy/Fixture/variadic.php.inc
@@ -6,6 +6,6 @@ sprintf('%s/%s', 'foo', 'bar');
 -----
 <?php
 
-sprintf(format: '%s/%s', values1: 'foo', values2: 'bar');
+sprintf('%s/%s', 'foo', 'bar');
 
 ?>
diff --git a/tests/DefaultStrategy/FixtureFunctions.php b/tests/DefaultStrategy/FixtureFunctions.php
new file mode 100644
index 0000000..efaccbb
--- /dev/null
+++ b/tests/DefaultStrategy/FixtureFunctions.php
@@ -0,0 +1,5 @@
+<?php
+
+declare(strict_types=1);
+
+function userlandVariadicFoo(string $command, string ...$values): void {}
diff --git a/tests/DefaultStrategy/config/rector.php b/tests/DefaultStrategy/config/rector.php
index a766f43..fe13f6b 100644
--- a/tests/DefaultStrategy/config/rector.php
+++ b/tests/DefaultStrategy/config/rector.php
@@ -5,6 +5,8 @@
 use Rector\Config\RectorConfig;
 use SavinMikhail\AddNamedArgumentsRector\AddNamedArgumentsRector;
 
+require_once __DIR__ . '/../FixtureFunctions.php';
+
 return RectorConfig::configure()
         ->withRules(rules: [
             AddNamedArgumentsRector::class,