diff --git a/csys/environ.lisp b/csys/environ.lisp
index c672aa4..4a1a643 100644
--- a/csys/environ.lisp
+++ b/csys/environ.lisp
@@ -65,7 +65,9 @@
 
 (defun find-cells (reg addr)
   (destructuring-bind (dom cat &optional (key "")) addr
-    (let ((idx (gethash (list dom cat) reg)))
-      (when idx
-        (index:query idx key)))))
+    (let* ((idx (gethash (list dom cat) reg))
+           (cells (when idx (index:query idx key))))
+      (unless cells
+        (util:lgw "not found" addr reg idx))
+      cells)))