diff --git a/lib/spack/spack/spec.py b/lib/spack/spack/spec.py
index 3c9a2729ecb..ee75b6fd097 100644
--- a/lib/spack/spack/spec.py
+++ b/lib/spack/spack/spec.py
@@ -52,6 +52,7 @@
 import enum
 import io
 import itertools
+import json
 import os
 import pathlib
 import platform
@@ -2145,7 +2146,9 @@ def spec_hash(self, hash):
         if hash.override is not None:
             return hash.override(self)
         node_dict = self.to_node_dict(hash=hash)
-        json_text = sjson.dump(node_dict)
+        json_text = json.dumps(
+            node_dict, ensure_ascii=True, indent=None, separators=(",", ":"), sort_keys=False
+        )
         # This implements "frankenhashes", preserving the last 7 characters of the
         # original hash when splicing so that we can avoid relocation issues
         out = spack.util.hash.b32_hash(json_text)