diff --git a/lib/spack/spack/package.py b/lib/spack/spack/package.py
index f1c7a824e63..de903c4ffaa 100644
--- a/lib/spack/spack/package.py
+++ b/lib/spack/spack/package.py
@@ -288,7 +288,7 @@ def determine_variants(cls, exes, version_str):
             # This function should not be overridden by subclasses,
             # as it is not designed for bespoke pkg detection but rather
             # on a per-platform basis
-            if hasattr(cls, 'platform_executables'):
+            if 'platform_executables' in cls.__dict__.keys():
                 raise PackageError("Packages should not override platform_executables")
             cls.platform_executables = platform_executables