diff --git a/src/Rules/Functions/CallToFunctionStatementWithoutSideEffectsRule.php b/src/Rules/Functions/CallToFunctionStatementWithoutSideEffectsRule.php
index e7d9c46156..a117c228fd 100644
--- a/src/Rules/Functions/CallToFunctionStatementWithoutSideEffectsRule.php
+++ b/src/Rules/Functions/CallToFunctionStatementWithoutSideEffectsRule.php
@@ -11,6 +11,7 @@
 use PHPStan\Rules\RuleErrorBuilder;
 use PHPStan\Type\NeverType;
 use PHPStan\Type\Type;
+use function count;
 use function in_array;
 use function sprintf;
 
@@ -65,6 +66,10 @@ public function processNode(Node $node, Scope $scope): array
 		}
 
 		$function = $this->reflectionProvider->getFunction($funcCall->name, $scope);
+		if (count($function->getAsserts()->getAsserts()) > 0) {
+			return [];
+		}
+
 		$functionName = $function->getName();
 		$functionHasSideEffects = !$function->hasSideEffects()->no();
 
diff --git a/src/Rules/Methods/CallToMethodStatementWithoutSideEffectsRule.php b/src/Rules/Methods/CallToMethodStatementWithoutSideEffectsRule.php
index 9b6adbdd14..e0a99028c2 100644
--- a/src/Rules/Methods/CallToMethodStatementWithoutSideEffectsRule.php
+++ b/src/Rules/Methods/CallToMethodStatementWithoutSideEffectsRule.php
@@ -13,6 +13,7 @@
 use PHPStan\Type\ErrorType;
 use PHPStan\Type\NeverType;
 use PHPStan\Type\Type;
+use function count;
 use function sprintf;
 
 /**
@@ -69,6 +70,9 @@ public function processNode(Node $node, Scope $scope): array
 		}
 
 		$method = $calledOnType->getMethod($methodName, $scope);
+		if (count($method->getAsserts()->getAsserts()) > 0) {
+			return [];
+		}
 
 		return [
 			RuleErrorBuilder::message(sprintf(
diff --git a/src/Rules/Methods/CallToStaticMethodStatementWithoutSideEffectsRule.php b/src/Rules/Methods/CallToStaticMethodStatementWithoutSideEffectsRule.php
index 31dc4dd096..2c80a25856 100644
--- a/src/Rules/Methods/CallToStaticMethodStatementWithoutSideEffectsRule.php
+++ b/src/Rules/Methods/CallToStaticMethodStatementWithoutSideEffectsRule.php
@@ -15,6 +15,7 @@
 use PHPStan\Type\NeverType;
 use PHPStan\Type\ObjectType;
 use PHPStan\Type\Type;
+use function count;
 use function sprintf;
 use function strtolower;
 
@@ -87,6 +88,10 @@ public function processNode(Node $node, Scope $scope): array
 			return [];
 		}
 
+		if (count($method->getAsserts()->getAsserts()) > 0) {
+			return [];
+		}
+
 		$methodResult = $scope->getType($staticCall);
 		if ($methodResult instanceof NeverType && $methodResult->isExplicit()) {
 			return [];
diff --git a/tests/PHPStan/Rules/Functions/CallToFunctionStatementWithoutSideEffectsRuleTest.php b/tests/PHPStan/Rules/Functions/CallToFunctionStatementWithoutSideEffectsRuleTest.php
index 28257e5a80..6d2fe2bbba 100644
--- a/tests/PHPStan/Rules/Functions/CallToFunctionStatementWithoutSideEffectsRuleTest.php
+++ b/tests/PHPStan/Rules/Functions/CallToFunctionStatementWithoutSideEffectsRuleTest.php
@@ -85,6 +85,11 @@ public function testPhpDoc(): void
 		]);
 	}
 
+	public function testBug12224(): void
+	{
+		$this->analyse([__DIR__ . '/data/bug-12224.php'], []);
+	}
+
 	public function testBug4455(): void
 	{
 		require_once __DIR__ . '/data/bug-4455.php';
diff --git a/tests/PHPStan/Rules/Functions/data/bug-12224.php b/tests/PHPStan/Rules/Functions/data/bug-12224.php
new file mode 100644
index 0000000000..9970576bca
--- /dev/null
+++ b/tests/PHPStan/Rules/Functions/data/bug-12224.php
@@ -0,0 +1,19 @@
+<?php declare(strict_types = 1);
+
+namespace Bug12224Function;
+
+/**
+ * @phpstan-pure
+ * @phpstan-assert string $value
+ */
+function string(mixed $value): string
+{
+	if (\is_string($value)) {
+		return $value;
+	}
+	throw new \RuntimeException();
+}
+
+/** @var string|null $a */
+$a = '';
+string($a);
diff --git a/tests/PHPStan/Rules/Methods/CallToMethodStatementWithoutSideEffectsRuleTest.php b/tests/PHPStan/Rules/Methods/CallToMethodStatementWithoutSideEffectsRuleTest.php
index a160bfcea7..e61f7a4aa6 100644
--- a/tests/PHPStan/Rules/Methods/CallToMethodStatementWithoutSideEffectsRuleTest.php
+++ b/tests/PHPStan/Rules/Methods/CallToMethodStatementWithoutSideEffectsRuleTest.php
@@ -111,6 +111,11 @@ public function testBug11503(): void
 		$this->analyse([__DIR__ . '/data/bug-11503.php'], $errors);
 	}
 
+	public function testBug12224(): void
+	{
+		$this->analyse([__DIR__ . '/data/bug-12224.php'], []);
+	}
+
 	public function testFirstClassCallables(): void
 	{
 		$this->analyse([__DIR__ . '/data/first-class-callable-method-without-side-effect.php'], [
diff --git a/tests/PHPStan/Rules/Methods/CallToStaticMethodStatementWithoutSideEffectsRuleTest.php b/tests/PHPStan/Rules/Methods/CallToStaticMethodStatementWithoutSideEffectsRuleTest.php
index bec56ff7d6..96dda15501 100644
--- a/tests/PHPStan/Rules/Methods/CallToStaticMethodStatementWithoutSideEffectsRuleTest.php
+++ b/tests/PHPStan/Rules/Methods/CallToStaticMethodStatementWithoutSideEffectsRuleTest.php
@@ -70,6 +70,11 @@ public function testBug4455(): void
 		$this->analyse([__DIR__ . '/data/bug-4455-static.php'], []);
 	}
 
+	public function testBug12224(): void
+	{
+		$this->analyse([__DIR__ . '/data/bug-12224.php'], []);
+	}
+
 	public function testFirstClassCallables(): void
 	{
 		$this->analyse([__DIR__ . '/data/first-class-callable-static-method-without-side-effect.php'], [
diff --git a/tests/PHPStan/Rules/Methods/data/bug-12224.php b/tests/PHPStan/Rules/Methods/data/bug-12224.php
new file mode 100644
index 0000000000..70664fee05
--- /dev/null
+++ b/tests/PHPStan/Rules/Methods/data/bug-12224.php
@@ -0,0 +1,35 @@
+<?php declare(strict_types = 1);
+
+namespace Bug12224Method;
+
+class Assert
+{
+	/**
+	 * @phpstan-pure
+	 * @phpstan-assert string $value
+	 */
+	public static function staticString(mixed $value): string
+	{
+		if (\is_string($value)) {
+			return $value;
+		}
+		throw new \RuntimeException();
+	}
+
+	/**
+	 * @phpstan-pure
+	 * @phpstan-assert string $value
+	 */
+	public function string(mixed $value): string
+	{
+		if (\is_string($value)) {
+			return $value;
+		}
+		throw new \RuntimeException();
+	}
+}
+
+/** @var string|null $a */
+$a = '';
+Assert::staticString($a);
+(new Assert())->string($a);