diff --git a/src/lualib/InstanceOf.ts b/src/lualib/InstanceOf.ts
index b856ddaa9..b75c040c2 100644
--- a/src/lualib/InstanceOf.ts
+++ b/src/lualib/InstanceOf.ts
@@ -8,7 +8,7 @@ function __TS__InstanceOf(this: void, obj: LuaClassInstance, classTbl: LuaClass)
         return !!classTbl[Symbol.hasInstance](obj);
     }
 
-    if (obj !== undefined) {
+    if (typeof obj === "object") {
         let luaClass = obj.constructor;
         while (luaClass !== undefined) {
             if (luaClass === classTbl) {
diff --git a/test/unit/classes/instanceof.spec.ts b/test/unit/classes/instanceof.spec.ts
index fdbb6e36e..4e4000153 100644
--- a/test/unit/classes/instanceof.spec.ts
+++ b/test/unit/classes/instanceof.spec.ts
@@ -49,6 +49,28 @@ test("null instanceof Class", () => {
     `.expectToMatchJsResult();
 });
 
+test("function instanceof Class", () => {
+    util.testFunction`
+        class myClass {}
+        const noop = () => {};
+        return (noop as any) instanceof myClass;
+    `.expectToMatchJsResult();
+});
+
+test("boolean instanceof Class", () => {
+    util.testFunction`
+        class myClass {}
+        return (false as any) instanceof myClass;
+    `.expectToMatchJsResult();
+});
+
+test("number instanceof Class", () => {
+    util.testFunction`
+        class myClass {}
+        return (5 as any) instanceof myClass;
+    `.expectToMatchJsResult();
+});
+
 test("instanceof export", () => {
     util.testModule`
         export class myClass {}