diff --git a/lib/spack/spack/schema/develop.py b/lib/spack/spack/schema/develop.py
index 13391dcdb0..8db1220e63 100644
--- a/lib/spack/spack/schema/develop.py
+++ b/lib/spack/spack/schema/develop.py
@@ -13,6 +13,7 @@
             r"\w[\w-]*": {
                 "type": "object",
                 "additionalProperties": False,
+                "required": ["spec"],
                 "properties": {"spec": {"type": "string"}, "path": {"type": "string"}},
             }
         },