diff --git a/lib/spack/spack/build_environment.py b/lib/spack/spack/build_environment.py
index c2a61280ef8..f1a1ce3dc8a 100644
--- a/lib/spack/spack/build_environment.py
+++ b/lib/spack/spack/build_environment.py
@@ -1269,6 +1269,8 @@ def make_stack(tb, stack=None):
             obj = frame.f_locals["self"]
             if isinstance(obj, spack.package_base.PackageBase):
                 break
+    else:
+        return None
 
     # We found obj, the Package implementation we care about.
     # Point out the location in the install method where we failed.