diff --git a/packages/Php/src/Rector/FuncCall/CountOnNullRector.php b/packages/Php/src/Rector/FuncCall/CountOnNullRector.php
index 6db49edffde4..78d58986a336 100644
--- a/packages/Php/src/Rector/FuncCall/CountOnNullRector.php
+++ b/packages/Php/src/Rector/FuncCall/CountOnNullRector.php
@@ -57,17 +57,7 @@ public function getNodeTypes(): array
      */
     public function refactor(Node $node): ?Node
     {
-        if (! $this->isName($node, 'count')) {
-            return null;
-        }
-
-        // check if it has some condition before already, if so, probably it's already handled
-        if ($node->getAttribute(self::ALREADY_CHANGED_ON_COUNT)) {
-            return null;
-        }
-
-        $parentNode = $node->getAttribute(AttributeKey::PARENT_NODE);
-        if ($parentNode instanceof Ternary) {
+        if ($this->shouldSkip($node)) {
             return null;
         }
 
@@ -82,14 +72,16 @@ public function refactor(Node $node): ?Node
 
         if ($this->isNullType($countedNode)) {
             $identicalNode = new Identical($countedNode, $this->createNull());
-            $node->setAttribute(self::ALREADY_CHANGED_ON_COUNT, true);
-
             $ternaryNode = new Ternary($identicalNode, new LNumber(0), $node);
         } else {
-            $conditionNode = new BooleanOr(
-                $this->createFunction('is_array', [new Arg($countedNode)]),
-                new Instanceof_($countedNode, new FullyQualified('Countable'))
-            );
+            if ($this->isAtLeastPhpVersion('7.3')) {
+                $conditionNode = new FuncCall(new Node\Name('is_countable'), [new Arg($countedNode)]);
+            } else {
+                $conditionNode = new BooleanOr(
+                    $this->createFunction('is_array', [new Arg($countedNode)]),
+                    new Instanceof_($countedNode, new FullyQualified('Countable'))
+                );
+            }
 
             $ternaryNode = new Ternary($conditionNode, $node, new LNumber(0));
         }
@@ -99,4 +91,20 @@ public function refactor(Node $node): ?Node
 
         return $ternaryNode;
     }
+
+    private function shouldSkip(FuncCall $funcCall): bool
+    {
+        if (! $this->isName($funcCall, 'count')) {
+            return true;
+        }
+
+        // check if it has some condition before already, if so, probably it's already handled
+        if ($funcCall->getAttribute(self::ALREADY_CHANGED_ON_COUNT)) {
+            return true;
+        }
+
+        $parentNode = $funcCall->getAttribute(AttributeKey::PARENT_NODE);
+
+        return $parentNode instanceof Ternary;
+    }
 }
diff --git a/packages/Php/tests/Rector/FuncCall/CountOnNullRector/CountOnNullRectorTest.php b/packages/Php/tests/Rector/FuncCall/CountOnNullRector/CountOnNullRectorTest.php
index 5ca4bcd3b8ea..b711160db2ef 100644
--- a/packages/Php/tests/Rector/FuncCall/CountOnNullRector/CountOnNullRectorTest.php
+++ b/packages/Php/tests/Rector/FuncCall/CountOnNullRector/CountOnNullRectorTest.php
@@ -2,9 +2,11 @@
 
 namespace Rector\Php\Tests\Rector\FuncCall\CountOnNullRector;
 
-use Rector\Php\Rector\FuncCall\CountOnNullRector;
 use Rector\Testing\PHPUnit\AbstractRectorTestCase;
 
+/**
+ * @covers \Rector\Php\Rector\FuncCall\CountOnNullRector
+ */
 final class CountOnNullRectorTest extends AbstractRectorTestCase
 {
     public function test(): void
@@ -21,8 +23,8 @@ public function test(): void
         ]);
     }
 
-    protected function getRectorClass(): string
+    protected function provideConfig(): string
     {
-        return CountOnNullRector::class;
+        return __DIR__ . '/rector_with_php71.yaml';
     }
 }
diff --git a/packages/Php/tests/Rector/FuncCall/CountOnNullRector/CountOnNullRectorWithPHP73Test.php b/packages/Php/tests/Rector/FuncCall/CountOnNullRector/CountOnNullRectorWithPHP73Test.php
new file mode 100644
index 000000000000..113b32478a0f
--- /dev/null
+++ b/packages/Php/tests/Rector/FuncCall/CountOnNullRector/CountOnNullRectorWithPHP73Test.php
@@ -0,0 +1,21 @@
+<?php declare(strict_types=1);
+
+namespace Rector\Php\Tests\Rector\FuncCall\CountOnNullRector;
+
+use Rector\Testing\PHPUnit\AbstractRectorTestCase;
+
+/**
+ * @covers \Rector\Php\Rector\FuncCall\CountOnNullRector
+ */
+final class CountOnNullRectorWithPHP73Test extends AbstractRectorTestCase
+{
+    public function test(): void
+    {
+        $this->doTestFiles([__DIR__ . '/Fixture/is_countable.php.inc']);
+    }
+
+    protected function provideConfig(): string
+    {
+        return __DIR__ . '/rector_with_php73.yaml';
+    }
+}
diff --git a/packages/Php/tests/Rector/FuncCall/CountOnNullRector/Fixture/is_countable.php.inc b/packages/Php/tests/Rector/FuncCall/CountOnNullRector/Fixture/is_countable.php.inc
new file mode 100644
index 000000000000..dcc07fdcc691
--- /dev/null
+++ b/packages/Php/tests/Rector/FuncCall/CountOnNullRector/Fixture/is_countable.php.inc
@@ -0,0 +1,27 @@
+<?php
+
+namespace Rector\Php\Tests\Rector\FuncCall\CountOnNullRector\Fixture;
+
+class IsCountable
+{
+    public function run($values)
+    {
+        $valueCount = count($values);
+    }
+}
+
+?>
+-----
+<?php
+
+namespace Rector\Php\Tests\Rector\FuncCall\CountOnNullRector\Fixture;
+
+class IsCountable
+{
+    public function run($values)
+    {
+        $valueCount = is_countable($values) ? count($values) : 0;
+    }
+}
+
+?>
diff --git a/packages/Php/tests/Rector/FuncCall/CountOnNullRector/rector_with_php71.yaml b/packages/Php/tests/Rector/FuncCall/CountOnNullRector/rector_with_php71.yaml
new file mode 100644
index 000000000000..a836ab78c154
--- /dev/null
+++ b/packages/Php/tests/Rector/FuncCall/CountOnNullRector/rector_with_php71.yaml
@@ -0,0 +1,5 @@
+parameters:
+    php_version_features: '7.1'
+
+services:
+    Rector\Php\Rector\FuncCall\CountOnNullRector: ~
diff --git a/packages/Php/tests/Rector/FuncCall/CountOnNullRector/rector_with_php73.yaml b/packages/Php/tests/Rector/FuncCall/CountOnNullRector/rector_with_php73.yaml
new file mode 100644
index 000000000000..0487ae1e8a04
--- /dev/null
+++ b/packages/Php/tests/Rector/FuncCall/CountOnNullRector/rector_with_php73.yaml
@@ -0,0 +1,5 @@
+parameters:
+    php_version_features: '7.3'
+
+services:
+    Rector\Php\Rector\FuncCall\CountOnNullRector: ~
diff --git a/src/Php/PhpVersionProvider.php b/src/Php/PhpVersionProvider.php
index 332d41722bbc..f28ff7f1969a 100644
--- a/src/Php/PhpVersionProvider.php
+++ b/src/Php/PhpVersionProvider.php
@@ -16,15 +16,15 @@ public function __construct(?string $phpVersionFeatures)
 
     public function provide(): string
     {
+        if ($this->phpVersionFeatures) {
+            return $this->phpVersionFeatures;
+        }
+
         // for tests
         if (defined('PHPUNIT_COMPOSER_INSTALL') || defined('__PHPUNIT_PHAR__')) {
             return '7.5';
         }
 
-        if ($this->phpVersionFeatures) {
-            return $this->phpVersionFeatures;
-        }
-
         return PHP_VERSION;
     }