diff --git a/Package.swift b/Package.swift
index 7654db0..756b01f 100644
--- a/Package.swift
+++ b/Package.swift
@@ -4,6 +4,12 @@ import PackageDescription
 
 let package = Package(
     name: "swift-builders",
+    platforms: [
+        .iOS(.v12),
+        .macOS(.v10_15),
+        .tvOS(.v12),
+        .watchOS(.v4),
+    ],
     products: [
         .library(name: "Builders", targets: ["Builders"]),
         .library(name: "BuildersTestSupport", targets: ["BuildersTestSupport"]),