thodg/cl-unix-cybernetics

diff --git a/core/operation.lisp b/core/operation.lisp
index 58d151b..4dc7531 100644
--- a/core/operation.lisp
+++ b/core/operation.lisp
@@ -92,7 +92,7 @@
                   :property property
                   :host (current-host)
                   :os os))
-         (push op operations)))
+         (pushnew (the operation op) operations)))
     (nreverse operations)))
 
 (defgeneric resource-op-properties (resource))