diff --git a/support/installer/composer.json b/support/installer/composer.json
index 9497d61aa..6e8186ec2 100644
--- a/support/installer/composer.json
+++ b/support/installer/composer.json
@@ -1,7 +1,7 @@
 {
 	"type": "composer-plugin",
 	"name": "heroku/installer-plugin",
-	"version": "1.7.1",
+	"version": "1.7.2",
 	"autoload": {
 		"psr-4": {
 			"Heroku\\Buildpack\\PHP\\": "src/"
@@ -13,6 +13,7 @@
 		"plugin-modifies-install-path": true
 	},
 	"require": {
-		"composer-plugin-api": "^2.3.0"
+		"composer-plugin-api": "^2.3.0",
+		"php": ">=7.1"
 	}
 }
diff --git a/support/installer/src/NoopDownloader.php b/support/installer/src/NoopDownloader.php
index 104212b70..5f521e493 100644
--- a/support/installer/src/NoopDownloader.php
+++ b/support/installer/src/NoopDownloader.php
@@ -24,12 +24,12 @@ public function getInstallationSource(): string
 		return "dist";
 	}
 	
-	public function download(PackageInterface $package, string $path, PackageInterface $prevPackage = null): PromiseInterface
+	public function download(PackageInterface $package, string $path, ?PackageInterface $prevPackage = null): PromiseInterface
 	{
 		return \React\Promise\resolve(null);
 	}
 	
-	public function prepare(string $type, PackageInterface $package, string $path, PackageInterface $prevPackage = null): PromiseInterface
+	public function prepare(string $type, PackageInterface $package, string $path, ?PackageInterface $prevPackage = null): PromiseInterface
 	{
 		return \React\Promise\resolve(null);
 	}
@@ -50,7 +50,7 @@ public function remove(PackageInterface $package, string $path): PromiseInterfac
 		return \React\Promise\resolve(null);
 	}
 	
-	public function cleanup(string $type, PackageInterface $package, string $path, PackageInterface $prevPackage = null): PromiseInterface
+	public function cleanup(string $type, PackageInterface $package, string $path, ?PackageInterface $prevPackage = null): PromiseInterface
 	{
 		return \React\Promise\resolve(null);
 	}