diff --git a/njvm.c b/njvm.c
index 2835de1..b2bd442 100644
--- a/njvm.c
+++ b/njvm.c
@@ -189,6 +189,12 @@ void execute(struct program program) {
             case DROP:
                 *stack.current = *stack.current - SIGN_EXTEND(IMMEDIATE(program.program[i]));
                 break;
+            case DUP:
+                temp = pop(stack);
+                push(stack, temp);
+                push(stack, temp);
+                break;
+      
         }
         if (debug == 1) printf("=== DEBUG: Stack after instruction %i ===\n", i);
         if (debug == 1) printStack(stack, fp);