diff --git a/testament/important_packages.nim b/testament/important_packages.nim
index a21ea41b70..59f3be0259 100644
--- a/testament/important_packages.nim
+++ b/testament/important_packages.nim
@@ -168,6 +168,7 @@ pkg "timezones"
 pkg "tiny_sqlite"
 pkg "unicodedb", "nim c -d:release -r tests/tests.nim"
 pkg "unicodeplus", "nim c -d:release -r tests/tests.nim"
+pkg "union", "nim c -r tests/treadme.nim", url = "https://github.com/alaviss/union"
 pkg "unpack"
 pkg "weave", "nimble test_gc_arc", useHead = true
 pkg "websocket", "nim c websocket.nim"