diff --git a/src/__tests__/__snapshots__/compiler.test.ts.snap b/src/__tests__/__snapshots__/compiler.test.ts.snap
deleted file mode 100644
index 824ecb42..00000000
--- a/src/__tests__/__snapshots__/compiler.test.ts.snap
+++ /dev/null
@@ -1,32 +0,0 @@
-// Vitest Snapshot v1, https://vitest.dev/guide/snapshot.html
-
-exports[`E2E Compiler Pipeline > Compiler can do tco 1`] = `
-"(module
- (type $0 (func (param i32 i32 i32) (result i32)))
- (memory $0 1 150)
- (export "buffer" (memory $0))
- (export "fib" (func $fib#15065))
- (func $fib#15065 (type $0) (param $0 i32) (param $1 i32) (param $2 i32) (result i32)
-  (if (result i32)
-   (local.get $0)
-   (then
-    (return_call $fib#15065
-     (i32.sub
-      (local.get $0)
-      (i32.const 1)
-     )
-     (local.get $2)
-     (i32.add
-      (local.get $1)
-      (local.get $2)
-     )
-    )
-   )
-   (else
-    (local.get $1)
-   )
-  )
- )
-)
-"
-`;
diff --git a/src/__tests__/compiler.test.ts b/src/__tests__/compiler.test.ts
index 33b27106..9cd0dbfd 100644
--- a/src/__tests__/compiler.test.ts
+++ b/src/__tests__/compiler.test.ts
@@ -1,8 +1,9 @@
 import { e2eVoidText, gcVoidText, tcoText } from "./fixtures/e2e-file.js";
 import { compile } from "../compiler.js";
-import { describe, expect, test } from "vitest";
+import { describe, expect, test, vi } from "vitest";
 import assert from "node:assert";
 import { getWasmFn, getWasmInstance } from "../lib/wasm.js";
+import * as rCallUtil from "../assembler/return-call.js";
 
 describe("E2E Compiler Pipeline", () => {
   test("Compiler can compile and run a basic void program", async (t) => {
@@ -37,8 +38,8 @@ describe("E2E Compiler Pipeline", () => {
   });
 
   test("Compiler can do tco", async (t) => {
-    const mod = await compile(tcoText);
-    mod.optimize();
-    t.expect(mod.emitText()).toMatchSnapshot();
+    const spy = vi.spyOn(rCallUtil, "returnCall");
+    await compile(tcoText);
+    t.expect(spy).toHaveBeenCalledTimes(1);
   });
 });
diff --git a/src/assembler.ts b/src/assembler.ts
index 481c92c9..91b530c2 100644
--- a/src/assembler.ts
+++ b/src/assembler.ts
@@ -21,6 +21,7 @@ import { HeapTypeRef } from "./lib/binaryen-gc/types.js";
 import { getExprType } from "./semantics/resolution/get-expr-type.js";
 import { Match, MatchCase } from "./syntax-objects/match.js";
 import { initExtensionHelpers } from "./assembler/extension-helpers.js";
+import { returnCall } from "./assembler/return-call.js";
 
 export const assemble = (ast: Expr) => {
   const mod = new binaryen.Module();
@@ -182,7 +183,7 @@ const compileCall = (opts: CompileExprOpts<Call>): number => {
   const returnType = mapBinaryenType(opts, expr.fn!.returnType!);
 
   if (isReturnExpr && id === expr.parentFn?.id) {
-    return mod.return_call(id, args, returnType);
+    return returnCall(mod, id, args, returnType);
   }
 
   return mod.call(id, args, returnType);
diff --git a/src/assembler/return-call.ts b/src/assembler/return-call.ts
new file mode 100644
index 00000000..820402a7
--- /dev/null
+++ b/src/assembler/return-call.ts
@@ -0,0 +1,11 @@
+import binaryen from "binaryen";
+import { ExpressionRef, TypeRef } from "../lib/binaryen-gc/types.js";
+
+export const returnCall = (
+  mod: binaryen.Module,
+  fnId: string,
+  args: ExpressionRef[],
+  returnType: TypeRef
+) => {
+  return mod.return_call(fnId, args, returnType);
+};