diff --git a/tests/PHPStan/Rules/Comparison/NumberComparisonOperatorsConstantConditionRuleTest.php b/tests/PHPStan/Rules/Comparison/NumberComparisonOperatorsConstantConditionRuleTest.php
index ae47818512..4d89a240be 100644
--- a/tests/PHPStan/Rules/Comparison/NumberComparisonOperatorsConstantConditionRuleTest.php
+++ b/tests/PHPStan/Rules/Comparison/NumberComparisonOperatorsConstantConditionRuleTest.php
@@ -231,4 +231,10 @@ public function testBug6467(): void
 		$this->analyse([__DIR__ . '/data/bug-6467.php'], []);
 	}
 
+	public function testBug6642(): void
+	{
+		$this->treatPhpDocTypesAsCertain = true;
+		$this->analyse([__DIR__ . '/data/bug-6642.php'], []);
+	}
+
 }
diff --git a/tests/PHPStan/Rules/Comparison/data/bug-6642.php b/tests/PHPStan/Rules/Comparison/data/bug-6642.php
new file mode 100644
index 0000000000..b8ae395d17
--- /dev/null
+++ b/tests/PHPStan/Rules/Comparison/data/bug-6642.php
@@ -0,0 +1,10 @@
+<?php declare(strict_types = 1);
+
+namespace Bug6642;
+
+$i = 0;
+foreach([1,2,3] as $n){
+	$bool = $i++ < 3;
+	if($bool){
+	}
+}