diff --git a/lib/spack/spack/solver/asp.py b/lib/spack/spack/solver/asp.py
index 9c785464553..f0fa41fb6e0 100644
--- a/lib/spack/spack/solver/asp.py
+++ b/lib/spack/spack/solver/asp.py
@@ -1395,10 +1395,6 @@ def define_version_constraints(self):
             if exact_match:
                 allowed_versions = exact_match
 
-            # don't bother restricting anything if all versions are allowed
-            if len(allowed_versions) == len(self.possible_versions[pkg_name]):
-                continue
-
             predicates = [fn.version(pkg_name, v) for v in allowed_versions]
 
             # version_satisfies(pkg, constraint) is true if and only if a
diff --git a/lib/spack/spack/test/concretize.py b/lib/spack/spack/test/concretize.py
index fa08eb8097a..e5cd8b162ad 100644
--- a/lib/spack/spack/test/concretize.py
+++ b/lib/spack/spack/test/concretize.py
@@ -501,6 +501,11 @@ def test_conflicts_in_spec(self, conflict_spec):
         with pytest.raises(spack.error.SpackError):
             s.concretize()
 
+    def test_conflict_in_all_directives_true(self):
+        s = Spec('when-directives-true')
+        with pytest.raises(spack.error.SpackError):
+            s.concretize()
+
     @pytest.mark.parametrize('spec_str', [
         'conflict@10.0%clang+foo'
     ])