diff --git a/phpstan/config.neon b/phpstan/config.neon
index 5ac2cd37b..f09a2e4b7 100644
--- a/phpstan/config.neon
+++ b/phpstan/config.neon
@@ -58,3 +58,9 @@ parameters:
         - Composer\Composer::VERSION
         - Composer\Composer::RELEASE_DATE
         - Composer\Composer::SOURCE_VERSION
+
+services:
+	-
+		class: Composer\PHPStan\ConfigReturnTypeExtension
+		tags:
+			- phpstan.broker.dynamicMethodReturnTypeExtension
diff --git a/src/Composer/PHPStan/ConfigReturnTypeExtension.php b/src/Composer/PHPStan/ConfigReturnTypeExtension.php
new file mode 100644
index 000000000..73f1764bc
--- /dev/null
+++ b/src/Composer/PHPStan/ConfigReturnTypeExtension.php
@@ -0,0 +1,50 @@
+<?php
+
+namespace Composer\PHPStan;
+
+use Composer\Config;
+use PhpParser\Node\Expr\MethodCall;
+use PHPStan\Analyser\Scope;
+use PHPStan\Reflection\MethodReflection;
+use PHPStan\Reflection\ParametersAcceptorSelector;
+use PHPStan\Type\ArrayType;
+use PHPStan\Type\BooleanType;
+use PHPStan\Type\Constant\ConstantStringType;
+use PHPStan\Type\DynamicMethodReturnTypeExtension;
+use PHPStan\Type\ObjectType;
+use PHPStan\Type\StringType;
+use PHPStan\Type\Type;
+use PHPStan\Type\TypeCombinator;
+
+final class ConfigReturnTypeExtension implements DynamicMethodReturnTypeExtension {
+
+    public function getClass(): string
+    {
+        return Config::class;
+    }
+
+    public function isMethodSupported(MethodReflection $methodReflection): bool
+    {
+        return strtolower($methodReflection->getName()) === 'get';
+    }
+
+    public function getTypeFromMethodCall(MethodReflection $methodReflection, MethodCall $methodCall, Scope $scope): Type
+    {
+        $args = $methodCall->getArgs();
+
+        if (count($args) < 1) {
+            return ParametersAcceptorSelector::selectSingle($methodReflection->getVariants())->getReturnType();
+        }
+
+        $keyType = $scope->getType($args[0]->value);
+        if ($keyType instanceof ConstantStringType) {
+            if ($keyType->getValue() == 'allow-plugins') {
+                return TypeCombinator::addNull(
+                    new ArrayType(new StringType(), new BooleanType())
+                );
+            }
+        }
+
+        return ParametersAcceptorSelector::selectSingle($methodReflection->getVariants())->getReturnType();
+    }
+}