diff --git a/tests/PHPStan/Rules/Comparison/ImpossibleCheckTypeFunctionCallRuleTest.php b/tests/PHPStan/Rules/Comparison/ImpossibleCheckTypeFunctionCallRuleTest.php
index d496edc9d6..605eb6a5f5 100644
--- a/tests/PHPStan/Rules/Comparison/ImpossibleCheckTypeFunctionCallRuleTest.php
+++ b/tests/PHPStan/Rules/Comparison/ImpossibleCheckTypeFunctionCallRuleTest.php
@@ -573,4 +573,18 @@ public function testConditionalTypesInference(): void
 		]);
 	}
 
+	public function testBug6697(): void
+	{
+		$this->checkAlwaysTrueCheckTypeFunctionCall = true;
+		$this->treatPhpDocTypesAsCertain = true;
+		$this->analyse([__DIR__ . '/data/bug-6697.php'], []);
+	}
+
+	public function testBug6443(): void
+	{
+		$this->checkAlwaysTrueCheckTypeFunctionCall = true;
+		$this->treatPhpDocTypesAsCertain = true;
+		$this->analyse([__DIR__ . '/data/bug-6443.php'], []);
+	}
+
 }
diff --git a/tests/PHPStan/Rules/Comparison/data/bug-6443.php b/tests/PHPStan/Rules/Comparison/data/bug-6443.php
new file mode 100644
index 0000000000..e9e4383463
--- /dev/null
+++ b/tests/PHPStan/Rules/Comparison/data/bug-6443.php
@@ -0,0 +1,23 @@
+<?php
+
+namespace Bug6443;
+
+/**
+ * String utilities for frequent tasks
+ */
+class StringUtils
+{
+	public static function stringify(
+		mixed $anyValue,
+		string $arrayConcatChar = ", "
+	): string {
+		// this cases are always empty strings
+		if ($anyValue === null || (is_array($anyValue) && !$anyValue)) {
+			return "";
+		}
+		if (is_array($anyValue)) {
+			return implode($arrayConcatChar, $anyValue);
+		}
+		return "blub";
+	}
+}
diff --git a/tests/PHPStan/Rules/Comparison/data/bug-6697.php b/tests/PHPStan/Rules/Comparison/data/bug-6697.php
new file mode 100644
index 0000000000..9aa89afafa
--- /dev/null
+++ b/tests/PHPStan/Rules/Comparison/data/bug-6697.php
@@ -0,0 +1,5 @@
+<?php
+
+namespace Bug6697;
+
+$result = \is_subclass_of( '\\My\\Namespace\\MyClass', '\\My\\Namespace\\MyBaseClass', true);