diff --git a/game-scripts-tests/this_in_lambda_in_object.ts b/game-scripts-tests/this_in_lambda_in_object.ts
new file mode 100644
index 0000000..7aa021a
--- /dev/null
+++ b/game-scripts-tests/this_in_lambda_in_object.ts
@@ -0,0 +1,26 @@
+// Since this is the thing being tested, we need to disable the ESLint rule instead.
+/* eslint-disable object-shorthand */
+
+export default ({ expect }: typeof import('vitest')) => {
+	const myObject = {
+		a: 0,
+		b: function () {
+			this.a++
+			return this.a
+		},
+		c: function (value: number = this.a) {
+			this.a = value + 1
+		},
+		d: function ({ value = this.a }: { value?: number }) {
+			this.a = value + 1
+		}
+	}
+
+	expect(myObject.a).toBe(0)
+	myObject.b()
+	expect(myObject.a).toBe(1)
+	myObject.c()
+	expect(myObject.a).toBe(2)
+	myObject.d({})
+	expect(myObject.a).toBe(3)
+}
diff --git a/src/processScript/transform.ts b/src/processScript/transform.ts
index 609f020..3d0cc98 100644
--- a/src/processScript/transform.ts
+++ b/src/processScript/transform.ts
@@ -749,10 +749,19 @@ export function transform(
 
 		if (object.type == `ObjectExpression`) {
 			for (const property of (object as ObjectExpression).properties) {
-				if (property.type != `ObjectMethod`)
+				if (property.type == `ObjectMethod`) {
+					thisIsReferenced ||= replaceAllThisWith(property, scope, thisId)
 					continue
+				}
+
+				if (property.type == `ObjectProperty` && property.value.type == `FunctionExpression`) {
+					// Replace in things like this: function (foo = this.a)
+					for (const param of property.value.params) {
+						thisIsReferenced ||= replaceAllThisWith(param, scope, thisId)
+					}
 
-				thisIsReferenced ||= replaceAllThisWith(property, scope, thisId)
+					thisIsReferenced ||= replaceAllThisWith(property.value.body, scope, thisId)
+				}
 			}
 		} else {
 			for (const element of (object as ArrayExpression).elements) {