diff --git a/lib/spack/spack/hash_types.py b/lib/spack/spack/hash_types.py
index 01e31bb465..e4a238a93b 100644
--- a/lib/spack/spack/hash_types.py
+++ b/lib/spack/spack/hash_types.py
@@ -18,19 +18,22 @@ class SpecHashDescriptor(object):
 
     We currently use different hashes for different use cases.
     """
-    def __init__(self, deptype=('link', 'run'), package_hash=False):
+    def __init__(self, deptype=('link', 'run'), package_hash=False, attr=None):
         self.deptype = dp.canonical_deptype(deptype)
         self.package_hash = package_hash
+        self.attr = attr
 
 
 #: Default Hash descriptor, used by Spec.dag_hash() and stored in the DB.
-dag_hash = SpecHashDescriptor(deptype=('link', 'run'), package_hash=False)
+dag_hash = SpecHashDescriptor(deptype=('link', 'run'), package_hash=False,
+                              attr='_hash')
 
 
 #: Hash descriptor that includes build dependencies.
 build_hash = SpecHashDescriptor(
-    deptype=('build', 'link', 'run'), package_hash=False)
+    deptype=('build', 'link', 'run'), package_hash=False, attr='_build_hash')
 
 
 #: Full hash used in build pipelines to determine when to rebuild packages.
-full_hash = SpecHashDescriptor(deptype=('link', 'run'), package_hash=True)
+full_hash = SpecHashDescriptor(deptype=('link', 'run'), package_hash=True,
+                               attr='_full_hash')
diff --git a/lib/spack/spack/spec.py b/lib/spack/spack/spec.py
index 009775acf4..6636f15c51 100644
--- a/lib/spack/spack/spec.py
+++ b/lib/spack/spack/spec.py
@@ -1305,7 +1305,7 @@ def _spec_hash(self, hash):
 
         return b32_hash
 
-    def _cached_hash(self, length, attr, hash):
+    def _cached_hash(self, hash, length=None):
         """Helper function for storing a cached hash on the spec.
 
         This will run _spec_hash() with the deptype and package_hash
@@ -1315,13 +1315,16 @@ def _cached_hash(self, length, attr, hash):
         Arguments:
             hash (SpecHashDescriptor): type of hash to generate.
         """
-        hash_string = getattr(self, attr, None)
+        if not hash.attr:
+            return self._spec_hash(hash)[:length]
+
+        hash_string = getattr(self, hash.attr, None)
         if hash_string:
             return hash_string[:length]
         else:
             hash_string = self._spec_hash(hash)
             if self.concrete:
-                setattr(self, attr, hash_string)
+                setattr(self, hash.attr, hash_string)
 
             return hash_string[:length]
 
@@ -1333,7 +1336,7 @@ def dag_hash(self, length=None):
         revise this to include more detailed provenance when the
         concretizer can more aggressievly reuse installed dependencies.
         """
-        return self._cached_hash(length, '_hash', ht.dag_hash)
+        return self._cached_hash(ht.dag_hash, length)
 
     def build_hash(self, length=None):
         """Hash used to store specs in environments.
@@ -1341,7 +1344,7 @@ def build_hash(self, length=None):
         This hash includes build dependencies, and we need to preserve
         them to be able to rebuild an entire environment for a user.
         """
-        return self._cached_hash(length, '_build_hash', ht.build_hash)
+        return self._cached_hash(ht.build_hash, length)
 
     def full_hash(self, length=None):
         """Hash  to determine when to rebuild packages in the build pipeline.
@@ -1352,7 +1355,7 @@ def full_hash(self, length=None):
 
         TODO: investigate whether to include build deps here.
         """
-        return self._cached_hash(length, '_full_hash', ht.full_hash)
+        return self._cached_hash(ht.full_hash, length)
 
     def dag_hash_bit_prefix(self, bits):
         """Get the first <bits> bits of the DAG hash as an integer type."""
@@ -1456,7 +1459,7 @@ def to_node_dict(self, hash=ht.dag_hash):
             d['dependencies'] = syaml_dict([
                 (name,
                  syaml_dict([
-                     ('hash', dspec.spec._spec_hash(hash)),
+                     ('hash', dspec.spec._cached_hash(hash)),
                      ('type', sorted(str(s) for s in dspec.deptypes))])
                  ) for name, dspec in sorted(deps.items())
             ])