diff --git a/src/main/java/me/topchetoeu/jscript/common/Instruction.java b/src/main/java/me/topchetoeu/jscript/common/Instruction.java
index 838049c..d846072 100644
--- a/src/main/java/me/topchetoeu/jscript/common/Instruction.java
+++ b/src/main/java/me/topchetoeu/jscript/common/Instruction.java
@@ -64,7 +64,8 @@ public class Instruction {
         GLOB_DEF(0x62),
 
         STACK_ALLOC(0x70),
-        STACK_FREE(0x71);
+        STACK_REALLOC(0x71),
+        STACK_FREE(0x72);
 
         private static final HashMap<Integer, Type> types = new HashMap<>();
         public final int numeric;
@@ -456,11 +457,14 @@ public class Instruction {
         return new Instruction(Type.OPERATION, op);
     }
 
-    public static Instruction stackAlloc(int i) {
-        return new Instruction(Type.STACK_ALLOC, i);
+    public static Instruction stackAlloc(int n) {
+        return new Instruction(Type.STACK_ALLOC, n);
     }
-    public static Instruction stackFree(int i) {
-        return new Instruction(Type.STACK_FREE, i);
+    public static Instruction stackRealloc(int n) {
+        return new Instruction(Type.STACK_REALLOC, n);
+    }
+    public static Instruction stackFree(int n) {
+        return new Instruction(Type.STACK_FREE, n);
     }
 
     @Override public String toString() {
diff --git a/src/main/java/me/topchetoeu/jscript/runtime/InstructionRunner.java b/src/main/java/me/topchetoeu/jscript/runtime/InstructionRunner.java
index 585a389..67badc2 100644
--- a/src/main/java/me/topchetoeu/jscript/runtime/InstructionRunner.java
+++ b/src/main/java/me/topchetoeu/jscript/runtime/InstructionRunner.java
@@ -505,7 +505,15 @@ public class InstructionRunner {
         int n = instr.get(0);
 
         for (var i = 0; i < n; i++) frame.locals.add(new Value[] { Value.UNDEFINED });
-        
+
+        frame.codePtr++;
+        return null;
+    }
+    private static Value execStackRealloc(Environment env, Instruction instr, Frame frame) {
+        int n = instr.get(0);
+
+        for (var i = frame.locals.size() - n; i < frame.locals.size(); i++) frame.locals.set(i, new Value[] { frame.locals.get(i)[0] });
+
         frame.codePtr++;
         return null;
     }
@@ -576,6 +584,7 @@ public class InstructionRunner {
             case GLOB_SET: return exexGlobSet(env, instr, frame);
 
             case STACK_ALLOC: return execStackAlloc(env, instr, frame);
+            case STACK_REALLOC: return execStackRealloc(env, instr, frame);
             case STACK_FREE: return execStackFree(env, instr, frame);
 
             default: throw EngineException.ofSyntax("Invalid instruction " + instr.type.name() + ".");