diff --git a/lib/spack/spack/package.py b/lib/spack/spack/package.py
index ab03368135..11e64e9061 100644
--- a/lib/spack/spack/package.py
+++ b/lib/spack/spack/package.py
@@ -678,7 +678,7 @@ def installed_upstream(self):
     @classmethod
     def possible_dependencies(
             cls, transitive=True, expand_virtuals=True, deptype='all',
-            visited=None, missing=None):
+            visited=None, missing=None, virtuals=None):
         """Return dict of possible dependencies of this package.
 
         Args:
@@ -691,6 +691,7 @@ def possible_dependencies(
                 far, mapped to their immediate dependencies' names.
             missing (dict, optional): dict to populate with packages and their
                 *missing* dependencies.
+            virtuals (set): if provided, populate with virtuals seen so far.
 
         Returns:
             (dict): dictionary mapping dependency names to *their*
@@ -727,6 +728,8 @@ def possible_dependencies(
 
             # expand virtuals if enabled, otherwise just stop at virtuals
             if spack.repo.path.is_virtual(name):
+                if virtuals is not None:
+                    virtuals.add(name)
                 if expand_virtuals:
                     providers = spack.repo.path.providers_for(name)
                     dep_names = [spec.name for spec in providers]
@@ -759,7 +762,8 @@ def possible_dependencies(
                     continue
 
                 dep_cls.possible_dependencies(
-                    transitive, expand_virtuals, deptype, visited, missing)
+                    transitive, expand_virtuals, deptype, visited, missing,
+                    virtuals)
 
         return visited
 
diff --git a/lib/spack/spack/solver/asp.py b/lib/spack/spack/solver/asp.py
index 9a80dbe83f..b102863446 100644
--- a/lib/spack/spack/solver/asp.py
+++ b/lib/spack/spack/solver/asp.py
@@ -346,6 +346,11 @@ def arch_defaults(self):
         self.fact(fn.arch_os_default(default_arch.os))
         self.fact(fn.arch_target_default(default_arch.target))
 
+    def virtual_providers(self, virtuals):
+        for vspec in virtuals:
+            providers = spack.repo.path.providers_for(vspec)
+            print("PROVIDE", providers, [type(t) for t in providers])
+
     def generate_asp_program(self, specs):
         """Write an ASP program for specs.
 
@@ -373,6 +378,7 @@ def generate_asp_program(self, specs):
         self.h1('General Constraints')
         self.compiler_defaults()
         self.arch_defaults()
+        self.virtual_providers(virtuals)
 
         self.h1('Package Constraints')
         for pkg in pkgs: