diff --git a/lib/spack/spack/spec.py b/lib/spack/spack/spec.py
index 15eef1a748d..9d1027dd0bb 100644
--- a/lib/spack/spack/spec.py
+++ b/lib/spack/spack/spec.py
@@ -4861,8 +4861,8 @@ def from_node_dict(cls, node):
                 spec.external_modules = node["external"]["module"]
                 if spec.external_modules is False:
                     spec.external_modules = None
-                spec.extra_attributes = node["external"].get(
-                    "extra_attributes", syaml.syaml_dict()
+                spec.extra_attributes = (
+                    node["external"].get("extra_attributes") or syaml.syaml_dict()
                 )
 
         # specs read in are concrete unless marked abstract