diff --git a/rector.php b/rector.php
index b145f79..3231b06 100644
--- a/rector.php
+++ b/rector.php
@@ -3,7 +3,7 @@
 declare(strict_types=1);
 
 use Rector\Config\RectorConfig;
-use Rector\PHPUnit\Set\PHPUnitSetList;
+use Rector\TypeDeclaration\Rector\ClassMethod\BoolReturnTypeFromBooleanStrictReturnsRector;
 
 return RectorConfig::configure()
     ->withPhpSets(php81: true)
@@ -15,8 +15,11 @@
         privatization: true,
         typeDeclarations: true
     )
-    ->withSets([
-        PHPUnitSetList::PHPUNIT_100,
+    ->withComposerBased(phpunit: true)
+    ->withSkip([
+        BoolReturnTypeFromBooleanStrictReturnsRector::class => [
+            __DIR__ . '/tests/FilterTest.php',
+        ],
     ])
     ->withParallel()
     ->withRootFiles()
diff --git a/src/Assert/Filter.php b/src/Assert/Filter.php
new file mode 100644
index 0000000..1a46930
--- /dev/null
+++ b/src/Assert/Filter.php
@@ -0,0 +1,45 @@
+<?php
+
+declare(strict_types=1);
+
+namespace ArrayLookup\Assert;
+
+use Closure;
+use InvalidArgumentException;
+use ReflectionFunction;
+use ReflectionMethod;
+use ReflectionNamedType;
+
+use function gettype;
+use function is_object;
+use function sprintf;
+
+final class Filter
+{
+    public static function boolean(callable $filter): void
+    {
+        if ($filter instanceof Closure) {
+            $reflection = new ReflectionFunction($filter);
+        } elseif (is_object($filter)) {
+            $reflection = new ReflectionMethod($filter, '__invoke');
+        } else {
+            throw new InvalidArgumentException(
+                sprintf('Expected Closure or invokable object, %s given', gettype($filter))
+            );
+        }
+
+        $returnType = $reflection->getReturnType();
+
+        if (! $returnType instanceof ReflectionNamedType) {
+            throw new InvalidArgumentException('Expected a bool return type on callable filter, null given');
+        }
+
+        $returnTypeName = $returnType->getName();
+        if ($returnTypeName !== 'bool') {
+            throw new InvalidArgumentException(sprintf(
+                'Expected a bool return type on callable filter, %s given',
+                $returnTypeName
+            ));
+        }
+    }
+}
diff --git a/src/AtLeast.php b/src/AtLeast.php
index dada2db..14c76de 100644
--- a/src/AtLeast.php
+++ b/src/AtLeast.php
@@ -4,6 +4,7 @@
 
 namespace ArrayLookup;
 
+use ArrayLookup\Assert\Filter;
 use Traversable;
 use Webmozart\Assert\Assert;
 
@@ -47,14 +48,13 @@ private static function atLeastFoundTimes(
     ): bool {
         // usage must be higher than 0
         Assert::greaterThan($maxCount, 0);
+        // filter must be a callable with bool return type
+        Filter::boolean($filter);
 
         $totalFound = 0;
         foreach ($data as $key => $datum) {
             $isFound = $filter($datum, $key);
 
-            // returns of callable must be bool
-            Assert::boolean($isFound);
-
             if (! $isFound) {
                 continue;
             }
diff --git a/src/Collector.php b/src/Collector.php
index 23eb475..6ad5ae9 100644
--- a/src/Collector.php
+++ b/src/Collector.php
@@ -4,6 +4,7 @@
 
 namespace ArrayLookup;
 
+use ArrayLookup\Assert\Filter;
 use Traversable;
 use Webmozart\Assert\Assert;
 
@@ -67,20 +68,22 @@ public function getResults(): array
         // ensure transform property is set early ->withTransform() method
         Assert::isCallable($this->transform);
 
-        $count          = 0;
-        $collectedData  = [];
-        $isCallableWhen = is_callable($this->when);
+        $count         = 0;
+        $collectedData = [];
+
+        if (is_callable($this->when)) {
+            // filter must be a callable with bool return type
+            Filter::boolean($this->when);
+        }
 
         foreach ($this->data as $key => $datum) {
-            if ($isCallableWhen) {
+            if ($this->when !== null) {
                 /**
                  * @var callable(mixed $datum, int|string|null $key): bool $when
                  */
                 $when    = $this->when;
                 $isFound = ($when)($datum, $key);
 
-                Assert::boolean($isFound);
-
                 if (! $isFound) {
                     continue;
                 }
diff --git a/src/Finder.php b/src/Finder.php
index c13c8a6..7fbeb37 100644
--- a/src/Finder.php
+++ b/src/Finder.php
@@ -5,6 +5,7 @@
 namespace ArrayLookup;
 
 use ArrayIterator;
+use ArrayLookup\Assert\Filter;
 use ArrayObject;
 use Traversable;
 use Webmozart\Assert\Assert;
@@ -24,12 +25,12 @@ final class Finder
      */
     public static function first(iterable $data, callable $filter, bool $returnKey = false): mixed
     {
+        // filter must be a callable with bool return type
+        Filter::boolean($filter);
+
         foreach ($data as $key => $datum) {
             $isFound = $filter($datum, $key);
 
-            // returns of callable must be bool
-            Assert::boolean($isFound);
-
             if (! $isFound) {
                 continue;
             }
@@ -71,6 +72,9 @@ public static function last(
         // ensure data is array for end(), key(), current(), prev() usage
         Assert::isArray($data);
 
+        // filter must be a callable with bool return type
+        Filter::boolean($filter);
+
         // Use end(), key(), current(), prev() usage instead of array_reverse()
         // to avoid immediatelly got "Out of memory" on many data
         // see https://3v4l.org/IHo2H vs https://3v4l.org/Wqejc
@@ -91,9 +95,6 @@ public static function last(
             $current = current($data);
             $isFound = $filter($current, $key);
 
-            // returns of callable must be bool
-            Assert::boolean($isFound);
-
             if (! $isFound) {
                 // go to previous row
                 prev($data);
@@ -133,12 +134,12 @@ public static function rows(
         $newKey     = 0;
         $totalFound = 0;
 
+        // filter must be a callable with bool return type
+        Filter::boolean($filter);
+
         foreach ($data as $key => $datum) {
             $isFound = $filter($datum, $key);
 
-            // returns of callable must be bool
-            Assert::boolean($isFound);
-
             if (! $isFound) {
                 continue;
             }
diff --git a/src/Only.php b/src/Only.php
index 83978fc..e296abd 100644
--- a/src/Only.php
+++ b/src/Only.php
@@ -4,6 +4,7 @@
 
 namespace ArrayLookup;
 
+use ArrayLookup\Assert\Filter;
 use Traversable;
 use Webmozart\Assert\Assert;
 
@@ -47,14 +48,13 @@ private static function onlyFoundTimes(
     ): bool {
         // usage must be higher than 0
         Assert::greaterThan($maxCount, 0);
+        // filter must be a callable with bool return type
+        Filter::boolean($filter);
 
         $totalFound = 0;
         foreach ($data as $key => $datum) {
             $isFound = $filter($datum, $key);
 
-            // returns of callable must be bool
-            Assert::boolean($isFound);
-
             if (! $isFound) {
                 continue;
             }
diff --git a/tests/FilterTest.php b/tests/FilterTest.php
new file mode 100644
index 0000000..ccebcd7
--- /dev/null
+++ b/tests/FilterTest.php
@@ -0,0 +1,71 @@
+<?php
+
+declare(strict_types=1);
+
+namespace ArrayLookup\Tests;
+
+use ArrayLookup\AtLeast;
+use InvalidArgumentException;
+use PHPUnit\Framework\TestCase;
+
+final class FilterTest extends TestCase
+{
+    public function testOnceWithFilterInvokableClass(): void
+    {
+        $data   = [1, 2, 3];
+        $filter = new class {
+            public function __invoke(int $datum): bool
+            {
+                return $datum === 1;
+            }
+        };
+
+        $this->assertTrue(AtLeast::once($data, $filter));
+    }
+
+    public function testOnceWithStringFilter(): void
+    {
+        $this->expectException(InvalidArgumentException::class);
+        $this->expectExceptionMessage('Expected Closure or invokable object, string given');
+
+        $data   = [1, 'f'];
+        $filter = 'is_string';
+
+        AtLeast::once($data, $filter);
+    }
+
+    public function testWithoutReturnTypeCallable(): void
+    {
+        $this->expectException(InvalidArgumentException::class);
+        $this->expectExceptionMessage('Expected a bool return type on callable filter, null given');
+
+        $data = [1, 2, 3];
+
+        // phpcs:disable
+        $filter = new class {
+            public function __invoke(int $datum)
+            {
+                return $datum === 1;
+            }
+        };
+        // phpcs:enable
+
+        AtLeast::once($data, $filter);
+    }
+
+    public function testWithNonBoolReturnTypeCallable(): void
+    {
+        $this->expectException(InvalidArgumentException::class);
+        $this->expectExceptionMessage('Expected a bool return type on callable filter, string given');
+
+        $data   = [1, 2, 3];
+        $filter = new class {
+            public function __invoke(int $datum): string
+            {
+                return 'test';
+            }
+        };
+
+        AtLeast::once($data, $filter);
+    }
+}