diff --git a/var/spack/repos/builtin/packages/argobots/package.py b/var/spack/repos/builtin/packages/argobots/package.py
index 8f967d020b..3db9014afb 100644
--- a/var/spack/repos/builtin/packages/argobots/package.py
+++ b/var/spack/repos/builtin/packages/argobots/package.py
@@ -21,7 +21,8 @@ class Argobots(AutotoolsPackage):
     maintainers = ['shintaro-iwasaki']
 
     version("master", branch="master")
-    version("1.0", sha256="36a0815f7bf99900a9c9c1eef61ef9b3b76aa2cfc4594a304f6c8c3296da8def")
+    version("1.0", sha256="36a0815f7bf99900a9c9c1eef61ef9b3b76aa2cfc4594a304f6c8c3296da8def",
+            preferred=True)
     version("1.0rc2", sha256="7496b8bd39930a548b01aa3b1fe8f8b582c272600ef6a05ddc4398cf21dc12a2")
     version("1.0rc1", sha256="2dc4487556dce602655a6535f501136f0edc3575708029c80b1af6dccd069ce7")
     version("1.0b1", sha256="480b85b0e8db288400088a57c2dc5639f556843b06b0492841920c38348a2a3e")