diff --git a/lib/spack/spack/package_base.py b/lib/spack/spack/package_base.py
index 42eab851aa3..d5b9320c8bd 100644
--- a/lib/spack/spack/package_base.py
+++ b/lib/spack/spack/package_base.py
@@ -697,9 +697,6 @@ class PackageBase(WindowsRPath, PackageViewMixin, metaclass=PackageMeta):
     #: Verbosity level, preserved across installs.
     _verbose = None
 
-    #: index of patches by sha256 sum, built lazily
-    _patches_by_hash = None
-
     #: Package homepage where users can find more information about the package
     homepage: Optional[str] = None