diff --git a/src/App.tsx b/src/App.tsx
index 40a1ab399..fe706920d 100644
--- a/src/App.tsx
+++ b/src/App.tsx
@@ -9,7 +9,12 @@ import { DebugPanel } from './components/DebugPanel'
 import { v4 as uuidv4 } from 'uuid'
 import { asyncLexer } from './lang/tokeniser'
 import { abstractSyntaxTree } from './lang/abstractSyntaxTree'
-import { _executor, ExtrudeGroup, SketchGroup } from './lang/executor'
+import {
+  _executor,
+  ProgramMemory,
+  ExtrudeGroup,
+  SketchGroup,
+} from './lang/executor'
 import CodeMirror from '@uiw/react-codemirror'
 import { langs } from '@uiw/codemirror-extensions-langs'
 import { linter, lintGutter } from '@codemirror/lint'
@@ -234,7 +239,7 @@ export function App() {
         }
         engineCommandManager.startNewSession()
         setEngineCommandManager(engineCommandManager)
-        _executor(
+        const programMemory = await _executor(
           _ast,
           {
             root: {
@@ -276,39 +281,28 @@ export function App() {
           engineCommandManager,
           { bodyType: 'root' },
           []
-        ).then(async (programMemory) => {
-          const { artifactMap, sourceRangeMap } =
-            await engineCommandManager.waitForAllCommands()
+        )
 
-          setArtifactMap({ artifactMap, sourceRangeMap })
-          engineCommandManager.onHover((id) => {
-            if (!id) {
-              setHighlightRange([0, 0])
-            } else {
-              const sourceRange = sourceRangeMap[id]
-              setHighlightRange(sourceRange)
-            }
-          })
-          engineCommandManager.onClick(({ id, type }) => {
-            setCursor2({ range: sourceRangeMap[id], type })
-          })
-          setProgramMemory(programMemory)
-          const geos = programMemory?.return
-            ?.map(({ name }: { name: string }) => {
-              const artifact = programMemory?.root?.[name]
-              if (
-                artifact.type === 'extrudeGroup' ||
-                artifact.type === 'sketchGroup'
-              ) {
-                return artifact
-              }
-              return null
-            })
-            .filter((a) => a) as (ExtrudeGroup | SketchGroup)[]
+        const { artifactMap, sourceRangeMap } =
+          await engineCommandManager.waitForAllCommands()
 
-          // console.log(programMemory)
-          setError()
+        setArtifactMap({ artifactMap, sourceRangeMap })
+        engineCommandManager.onHover((id) => {
+          if (!id) {
+            setHighlightRange([0, 0])
+          } else {
+            const sourceRange = sourceRangeMap[id]
+            setHighlightRange(sourceRange)
+          }
         })
+        engineCommandManager.onClick(({ id, type }) => {
+          setCursor2({ range: sourceRangeMap[id], type })
+        })
+        if (programMemory !== undefined) {
+          setProgramMemory(programMemory)
+        }
+
+        setError()
       } catch (e: any) {
         if (e instanceof KCLError) {
           addKCLError(e)
diff --git a/src/lang/executor.test.ts b/src/lang/executor.test.ts
index 5d1b9dcdc..875224c19 100644
--- a/src/lang/executor.test.ts
+++ b/src/lang/executor.test.ts
@@ -6,6 +6,7 @@ import { ProgramMemory, Path, SketchGroup } from './executor'
 import { initPromise } from './rust'
 import { enginelessExecutor } from '../lib/testHelpers'
 import { vi } from 'vitest'
+import { KCLUndefinedValueError } from './errors'
 
 beforeAll(() => initPromise)
 
@@ -440,6 +441,22 @@ describe('testing math operators', () => {
   })
 })
 
+describe('Testing Errors', () => {
+  it('should throw an error when a variable is not defined', async () => {
+    const code = `const myVar = 5
+const theExtrude = startSketchAt([0, 0])
+  |> line([-2.4, 5], %)
+  |> line([-0.76], myVarZ, %)
+  |> line([5,5], %)
+  |> close(%)
+  |> extrude(4, %)
+show(theExtrude)`
+    await expect(exe(code)).rejects.toEqual(
+      new KCLUndefinedValueError('Memory item myVarZ not found', [[100, 106]])
+    )
+  })
+})
+
 // helpers
 
 async function exe(
diff --git a/src/lang/executor.ts b/src/lang/executor.ts
index 83361e7df..abf1edb00 100644
--- a/src/lang/executor.ts
+++ b/src/lang/executor.ts
@@ -222,9 +222,11 @@ export const _executor = async (
   }
   const { body } = node
   const proms: Promise<any>[] = []
-  body.forEach(async (statement, bodyIndex) => {
+  for (let bodyIndex = 0; bodyIndex < body.length; bodyIndex++) {
+    const statement = body[bodyIndex]
     if (statement.type === 'VariableDeclaration') {
-      statement.declarations.forEach(async (declaration, index) => {
+      for (let index = 0; index < statement.declarations.length; index++) {
+        const declaration = statement.declarations[index]
         const variableName = declaration.id.name
         const pathToNode: PathToNode = [
           ...previousPathToNode,
@@ -520,7 +522,7 @@ export const _executor = async (
             [[declaration.start, declaration.end]]
           )
         }
-      })
+      }
     } else if (statement.type === 'ExpressionStatement') {
       const expression = statement.expression
       if (expression.type === 'CallExpression') {
@@ -560,7 +562,7 @@ export const _executor = async (
         _programMemory.return = await prom
       }
     }
-  })
+  }
   await Promise.all(proms)
   return _programMemory
 }