diff --git a/lib/spack/spack/concretize.py b/lib/spack/spack/concretize.py
index 805604368ec..3f569f9dce3 100644
--- a/lib/spack/spack/concretize.py
+++ b/lib/spack/spack/concretize.py
@@ -68,8 +68,9 @@ def concretize_version(self, spec):
         # If there are known avaialble versions, return the most recent
         # version that satisfies the spec
         pkg = spec.package
-        valid_versions = [v for v in pkg.versions
-                          if any(v.satisfies(sv) for sv in spec.versions)]
+        valid_versions = sorted(
+            [v for v in pkg.versions
+             if any(v.satisfies(sv) for sv in spec.versions)])
 
         if valid_versions:
             spec.versions = ver([valid_versions[-1]])