diff --git a/src/arboretum/dengine/node.clj b/src/arboretum/dengine/node.clj
index 2891041..486acc9 100644
--- a/src/arboretum/dengine/node.clj
+++ b/src/arboretum/dengine/node.clj
@@ -32,10 +32,17 @@
 (defn make-node 
   "Make a node. TODO: these wrapper functions will probably disappear once
    I'm more comfortable with the architecture."
-  ([feature ^Boolean colour ^String fragment]
-   (make-node feature colour fragment nil))
-  ([feature ^Boolean colour ^String fragment children ]
-  (NodeImpl. feature colour fragment children)))
+  ([feature-id ^Boolean colour ^String fragment]
+   (make-node feature-id colour fragment nil))
+  ([feature-id ^Boolean colour ^String fragment children ]
+  (if (and (find-feature-for @!kb feature-id)
+             (every? #(satisfies? Node %) children))
+    (NodeImpl. feature-id colour fragment children)
+    (throw (ex-info "Unexpected item passed as child node"
+                    {:feature-id feature-id
+                     :colour colour
+                     :fragment fragment
+                     :children children})))))
 
 ;; Here's the algorithm as published in A Graphical Inference Mechanism, 
 ;; but it's not real Interlisp code, and I remember there being at least