diff --git a/dist/host/sandbox.js b/dist/host/sandbox.js
index 78cf1e6..6a5e085 100644
--- a/dist/host/sandbox.js
+++ b/dist/host/sandbox.js
@@ -103,9 +103,11 @@ class Sandbox {
     }
     async execute({ code, timeout, globals, context, }) {
         this.start();
-        const result = await this.initialize({ timeout });
-        if (result.error) {
-            return result;
+        if(!this.initialized) { 
+            const result = await this.initialize({ timeout });
+            if (result.error) {
+                return result;
+            }
         }
         return new Promise((resolve) => {
             this.queue.push({
@@ -117,7 +119,6 @@ class Sandbox {
                 context: context ?? {},
                 output: [],
                 callback: (res) => {
-                    this.initialized = false;
                     resolve(res);
                 },
             });
diff --git a/dist/sandbox/runtime.js b/dist/sandbox/runtime.js
index 0c333dd..48e1352 100644
--- a/dist/sandbox/runtime.js
+++ b/dist/sandbox/runtime.js
@@ -32,8 +32,16 @@ environment.define = (name) => {
 };
 environment.defineAsync = (name) => {
     environment[name] = (...args) => {
-        const callback = args.pop();
-        return environment.dispatch(name, args, callback);
+        if (typeof args[args.length-1] == 'function') { // water-fall function
+            let callback = args.pop();
+            return environment.dispatch(name, args, callback);
+        }else {
+            return new Promise(async(resolve, reject) => { // standard await function
+                environment.dispatch(name, args, function(value) {
+                    resolve(value);
+                })
+            })
+        }
     };
 };
 const chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/';
diff --git a/vanesca-tests/fix1.js b/vanesca-tests/fix1.js
new file mode 100644
index 0000000..6a19b49
--- /dev/null
+++ b/vanesca-tests/fix1.js
@@ -0,0 +1,28 @@
+
+process.stdout.write("\u001b[2J\u001b[00H") // clear screen
+const { Sandbox, SandboxCluster } = require('../v8-sandbox')
+let sandbox = new Sandbox({ memory: 1000, require: __dirname + '/functions1.js' })
+
+let code = `
+    async function test() {
+
+        // always works! (water-fall/callback embedded)
+        addNumbers(1, 2, function(result) {
+            if(result.error) console.log('error1:', result.error)
+            if(result.value) console.log('value1:', result.value)
+        })
+
+        // only works with the runtime.js fix (standard await)
+        // otherwise the last argument is removed, because it expects a callback (embedded)
+        let {error, value} = await addNumbers(1, 2)
+        if(error) console.log('error2:', error)
+        if(value) console.log('value2:', value)
+    }
+    test()
+`; // always end with semicolon
+
+(async () => {
+
+    // test 1 (runs in async)
+    await sandbox.execute({ code })
+})()
\ No newline at end of file
diff --git a/vanesca-tests/fix2.js b/vanesca-tests/fix2.js
new file mode 100644
index 0000000..546cd24
--- /dev/null
+++ b/vanesca-tests/fix2.js
@@ -0,0 +1,56 @@
+
+process.stdout.write("\u001b[2J\u001b[00H") // clear screen
+const { Sandbox, SandboxCluster } = require('../v8-sandbox')
+let sandbox = new Sandbox({ memory: 1000 })
+
+let code1 = `
+    let t = 1
+    console.log(t) // works
+`; // always end with semicolon
+
+let code2 = ` // repeated executes STACK and should keep their values
+    t++
+    console.log(t)
+`;
+
+(async () => {
+
+    const RUN = 4
+    console.log('Test no.' + RUN)
+
+    // test 1 (runs in sync) (works)
+    if(RUN === 1) {
+        sandbox.execute({ code: code1 })
+        sandbox.execute({ code: code2 })
+    }
+
+    //////////////////////////////////////////
+
+    // test 2 (runs first in async/second sync) (doesn't work, even though it should!)
+    if(RUN === 2) {
+        await sandbox.execute({ code: code1 })
+        sandbox.execute({ code: code2 })
+    }
+
+    //////////////////////////////////////////
+
+    // test 3 (run in async) (doesn't work, even though it should!)
+    if(RUN === 3) {
+        await sandbox.execute({ code: code1 })
+        await sandbox.execute({ code: code2 })
+    }
+
+    //////////////////////////////////////////
+
+    // test 4 (promise result also doesn't work, even though it should!)
+    if(RUN === 4) {
+        sandbox.execute({ code: code1 }).then(() =>
+            // doesn't work, even though it should!
+            // because of a flag being reset in sandbox.js code
+            // this is fixed now.
+            setTimeout(async() => {
+               sandbox.execute({ code: code2 }) // should display '2' (after fix)
+            }, 2000)
+        )
+    }
+})()
\ No newline at end of file
diff --git a/vanesca-tests/functions1.js b/vanesca-tests/functions1.js
new file mode 100644
index 0000000..d9951fd
--- /dev/null
+++ b/vanesca-tests/functions1.js
@@ -0,0 +1,10 @@
+
+// Create or require your own functions and libraries (more safe)
+
+// Async (water-fall method / callback)
+defineAsync('addNumbers', ([ value1, value2 ], { respond, callback }) => {
+    respond() // always required!
+    setTimeout(() => {
+        callback({error: null, value: value1 + value2}) // send to sandbox
+    }, 1000) // 1 sec delay (for testing)
+})
\ No newline at end of file