diff --git a/wip-duuqnd/user-side-compiler/instruction.lisp b/wip-duuqnd/user-side-compiler/instruction.lisp
index 8e0a599..16c9e61 100644
--- a/wip-duuqnd/user-side-compiler/instruction.lisp
+++ b/wip-duuqnd/user-side-compiler/instruction.lisp
@@ -85,16 +85,19 @@
     `(progn
        (defclass ,base-name (instruction)
          ((%mnemonic :allocation :class :initform ',mnemonic)))
+       (setf (slot-value (make-instance ',base-name) '%mnemonic) ',mnemonic)
        ,@(loop :for (mode code) :in modes-and-codes
-               :collect `(defclass ,(intern (format nil "INST-~A-~A"
-                                                    name mode))
-                             ,(append
-                               `(,base-name
-                                 ,(addressing-mode-to-class-name mode)
-                                 complete-mixin)
-                               (when branching-p
-                                 '(branching-mixin)))
-                           ((%opcode :allocation :class :initform ,code)))))))
+               :for class-name := (intern (format nil "INST-~A-~A" name mode))
+               :collect `(progn
+                           (defclass ,class-name
+                               ,(append
+                                 `(,base-name
+                                   ,(addressing-mode-to-class-name mode)
+                                   complete-instruction-mixin)
+                                 (when branching-p
+                                   '(branching-mixin)))
+                             ((%opcode :allocation :class :initform ,code)))
+                           (setf (slot-value (allocate-instance (find-class ',class-name)) '%opcode) ,code))))))
 
 (defun fix-label-addresses-in-instruction-list (instruction-list origin)
   (loop :with address := origin
@@ -106,23 +109,22 @@
 
 ;;; Testing
 
-(define-instruction "TXA" nil (:implied 0))
-(define-instruction "PHA" nil (:implied 0))
-(define-instruction "PLA" nil (:implied 0))
-(define-instruction "TAX" nil (:implied 0))
-(define-instruction "DEX" nil (:implied 0))
-(define-instruction "BNE" t (:relative 0))
+(define-instruction "TXA" nil (:implied #x8a))
+(define-instruction "PHA" nil (:implied #x48))
+(define-instruction "PLA" nil (:implied #x68))
+(define-instruction "TAX" nil (:implied #xaa))
+(define-instruction "DEX" nil (:implied #xca))
+(define-instruction "BNE" t (:relative #xd0))
 (define-instruction "LDA" nil
-  (:absolute 0)
-  (:zero-page 0)
-  (:immediate 0)
-  (:absolute-y 0))
+  (:immediate #xa9)
+  (:zero-page #xa5)
+  (:absolute #xad)
+  (:absolute-y #xb9))
 (define-instruction "LDY" nil
-  (:absolute 0)
-  (:immediate 0))
+  (:immediate #xa0)
+  (:absolute #xac))
 (define-instruction "STA" nil
-  (:absolute 0)
-  (:immediate 0)
-  (:absolute-y 0))
+  (:absolute #x8d)
+  (:absolute-y #x99))
 (define-instruction "JSR" nil
-  (:absolute 0))
+  (:absolute #x20))