diff --git a/lib/spack/spack/solver/asp.py b/lib/spack/spack/solver/asp.py
index f26a83f9e2..3730bc6e38 100644
--- a/lib/spack/spack/solver/asp.py
+++ b/lib/spack/spack/solver/asp.py
@@ -95,7 +95,7 @@ def default_clingo_control():
     control = clingo().Control()
     control.configuration.configuration = "tweety"
     control.configuration.solver.heuristic = "Domain"
-    control.configuration.solver.opt_strategy = "usc,one"
+    control.configuration.solver.opt_strategy = "usc,one,1"
     return control
 
 
diff --git a/lib/spack/spack/solver/heuristic.lp b/lib/spack/spack/solver/heuristic.lp
index 1bace84312..1f31d7eae0 100644
--- a/lib/spack/spack/solver/heuristic.lp
+++ b/lib/spack/spack/solver/heuristic.lp
@@ -8,12 +8,12 @@
 %=============================================================================
 
 % No duplicates by default (most of them will be true)
-#heuristic attr("node",         node(1..X-1, Package)) : max_dupes(Package, X), not virtual(Package), X > 1. [50, false]
-#heuristic attr("virtual_node", node(1..X-1, Package)) : max_dupes(Package, X), virtual(Package)    , X > 1. [50, false]
+#heuristic attr("node",         node(1..X-1, Package)) : max_dupes(Package, X), not virtual(Package), X > 1. [100, false]
+#heuristic attr("virtual_node", node(1..X-1, Package)) : max_dupes(Package, X), virtual(Package)    , X > 1. [100, false]
 
 % Pick preferred version
 #heuristic attr("version", node(PackageID, Package), Version) : pkg_fact(Package, version_declared(Version, 0     )), attr("node", node(PackageID, Package)).             [40, true]
-#heuristic attr("version", node(PackageID, Package), Version) : pkg_fact(Package, version_declared(Version, Weight)), attr("node", node(PackageID, Package)), Weight > 0. [40, false]
+#heuristic attr("version", node(PackageID, Package), Version) : pkg_fact(Package, version_declared(Version, Weight)), attr("node", node(PackageID, Package)), Weight > 0. [40+5*Weight, false]
 #heuristic version_weight(node(PackageID, Package), 0)        : pkg_fact(Package, version_declared(Version, 0     )), attr("node", node(PackageID, Package)).             [40, true]
 
 % Use default variants