diff --git a/src/Rules/Comparison/ImpossibleCheckTypeHelper.php b/src/Rules/Comparison/ImpossibleCheckTypeHelper.php
index 43d2532c98..a49038600a 100644
--- a/src/Rules/Comparison/ImpossibleCheckTypeHelper.php
+++ b/src/Rules/Comparison/ImpossibleCheckTypeHelper.php
@@ -170,6 +170,10 @@ public function findSpecifiedType(
 				return true;
 			}
 
+			if ($expr instanceof Expr\Variable && is_string($expr->name) && !$scope->hasVariableType($expr->name)->yes()) {
+				return true;
+			}
+
 			return (
 				$node instanceof FuncCall
 				|| $node instanceof MethodCall
diff --git a/tests/PHPStan/Rules/Comparison/ImpossibleCheckTypeFunctionCallRuleTest.php b/tests/PHPStan/Rules/Comparison/ImpossibleCheckTypeFunctionCallRuleTest.php
index 5a471e0a19..8e7633a5df 100644
--- a/tests/PHPStan/Rules/Comparison/ImpossibleCheckTypeFunctionCallRuleTest.php
+++ b/tests/PHPStan/Rules/Comparison/ImpossibleCheckTypeFunctionCallRuleTest.php
@@ -406,4 +406,11 @@ public function testBug4657(): void
 		$this->analyse([__DIR__ . '/data/bug-4657.php'], []);
 	}
 
+	public function testBug4999(): void
+	{
+		$this->checkAlwaysTrueCheckTypeFunctionCall = true;
+		$this->treatPhpDocTypesAsCertain = false;
+		$this->analyse([__DIR__ . '/data/bug-4999.php'], []);
+	}
+
 }
diff --git a/tests/PHPStan/Rules/Comparison/data/bug-4999.php b/tests/PHPStan/Rules/Comparison/data/bug-4999.php
new file mode 100644
index 0000000000..ee2af8c7f6
--- /dev/null
+++ b/tests/PHPStan/Rules/Comparison/data/bug-4999.php
@@ -0,0 +1,25 @@
+<?php declare(strict_types = 1);
+
+namespace Bug4999;
+
+class HelloWorld
+{
+	/**
+	 * @param mixed[] $array
+	 */
+	public function extractPhone(array $array): void
+	{
+		$phone = null;
+
+		if (array_key_exists('PHONE', $array)) {
+			while (null === $phone && is_array($value = array_shift($array['PHONE']))) {
+				$phone = self::parsePhone($value['VALUE']);
+			}
+		}
+	}
+
+	private static function parsePhone($something): ?string
+	{
+		return null === $something ? null : '911';
+	}
+}