diff --git a/bin/wasmoon b/bin/wasmoon
index 2bcf6cb..9100384 100755
--- a/bin/wasmoon
+++ b/bin/wasmoon
@@ -76,7 +76,7 @@ async function main() {
             input: process.stdin,
             output: process.stdout,
             terminal: true,
-            removeHistoryDuplicates: true
+            removeHistoryDuplicates: true,
         })
 
         rl.prompt()
@@ -91,8 +91,7 @@ async function main() {
 
             const result = luamodule.lua_pcallk(lua.global.address, 0, LUA_MULTRET, 0, 0, null)
             if (result === LuaReturn.Ok) {
-                const returnValues = Array.from({ length: lua.global.getTop() })
-                    .map((_, i) => lua.global.indexToString(i + 1))
+                const returnValues = Array.from({ length: lua.global.getTop() }).map((_, i) => lua.global.indexToString(i + 1))
 
                 if (returnValues.length) {
                     console.log(...returnValues)
@@ -109,7 +108,7 @@ async function main() {
     }
 }
 
-main().catch(err => {
+main().catch((err) => {
     console.error(err)
     process.exit(1)
 })
diff --git a/src/engine.ts b/src/engine.ts
index f8875e2..5a55a7b 100755
--- a/src/engine.ts
+++ b/src/engine.ts
@@ -86,7 +86,7 @@ export default class LuaEngine {
                 // Move all stack results to the global state to avoid referencing the thread values
                 // which will be cleaned up in the finally below.
                 this.cmodule.lua_xmove(thread.address, this.global.address, result.length)
-                // The shenanigans here are to return the first reuslt value on the stack.
+                // The shenanigans here are to return the first result value on the stack.
                 // Say there's 2 values at stack indexes 1 and 2. Then top is 2, result.length is 2.
                 // That's why there's a + 1 sitting at the end.
                 return this.global.getValue(this.global.getTop() - result.length + 1)
diff --git a/src/type-extensions/promise.ts b/src/type-extensions/promise.ts
index 160c463..f37718f 100644
--- a/src/type-extensions/promise.ts
+++ b/src/type-extensions/promise.ts
@@ -1,6 +1,7 @@
 import { Decoration } from '../decoration'
 import { LuaReturn, LuaState } from '../types'
 import { decorateFunction } from './function'
+import { isPromise } from '../utils'
 import Global from '../global'
 import MultiReturn from '../multireturn'
 import RawResult from '../raw-result'
@@ -34,8 +35,8 @@ class PromiseTypeExtension<T = unknown> extends TypeExtension<Promise<T>> {
             thread.lua.lua_setfield(thread.address, metatableIndex, '__gc')
 
             const checkSelf = (self: Promise<any>): true => {
-                if (Promise.resolve(self) !== self && typeof self.then !== 'function') {
-                    throw new Error('promise method called without self instance')
+                if (!isPromise(self)) {
+                    throw new Error('self instance is not a promise')
                 }
                 return true
             }
@@ -131,7 +132,7 @@ class PromiseTypeExtension<T = unknown> extends TypeExtension<Promise<T>> {
     }
 
     public pushValue(thread: Thread, decoration: Decoration<Promise<T>>): boolean {
-        if (Promise.resolve(decoration.target) !== decoration.target && typeof decoration.target?.then !== 'function') {
+        if (!isPromise(decoration.target)) {
             return false
         }
         return super.pushValue(thread, decoration)
diff --git a/src/type-extensions/proxy.ts b/src/type-extensions/proxy.ts
index 3797b73..5bc1301 100644
--- a/src/type-extensions/proxy.ts
+++ b/src/type-extensions/proxy.ts
@@ -1,6 +1,7 @@
 import { BaseDecorationOptions, Decoration } from '../decoration'
 import { LuaReturn, LuaState, LuaType } from '../types'
 import { decorateFunction } from './function'
+import { isPromise } from '../utils'
 import Global from '../global'
 import MultiReturn from '../multireturn'
 import Thread from '../thread'
@@ -150,7 +151,7 @@ class ProxyTypeExtension extends TypeExtension<any, ProxyDecorationOptions> {
                 }
             }
 
-            if (Promise.resolve(target) === target || typeof target.then === 'function') {
+            if (isPromise(target)) {
                 return false
             }
         } else if (options.proxy === false) {
diff --git a/src/utils.ts b/src/utils.ts
new file mode 100644
index 0000000..68b54c0
--- /dev/null
+++ b/src/utils.ts
@@ -0,0 +1,3 @@
+export const isPromise = (target: any): target is Promise<unknown> => {
+    return target && (Promise.resolve(target) === target || typeof target.then === 'function')
+}