diff --git a/js/repl.ts b/js/repl.ts
index ae457e8e45..075affc103 100644
--- a/js/repl.ts
+++ b/js/repl.ts
@@ -28,7 +28,7 @@ function startRepl(historyFile: string): number {
 }
 
 // @internal
-export function readline(rid: number, prompt: string): string {
+export async function readline(rid: number, prompt: string): Promise<string> {
   const builder = flatbuffers.createBuilder();
   const prompt_ = builder.createString(prompt);
   msg.ReplReadline.startReplReadline(builder);
@@ -36,8 +36,11 @@ export function readline(rid: number, prompt: string): string {
   msg.ReplReadline.addPrompt(builder, prompt_);
   const inner = msg.ReplReadline.endReplReadline(builder);
 
-  // TODO use async?
-  const baseRes = dispatch.sendSync(builder, msg.Any.ReplReadline, inner);
+  const baseRes = await dispatch.sendAsync(
+    builder,
+    msg.Any.ReplReadline,
+    inner
+  );
 
   assert(baseRes != null);
   assert(msg.Any.ReplReadlineRes === baseRes!.innerType());
@@ -49,7 +52,7 @@ export function readline(rid: number, prompt: string): string {
 }
 
 // @internal
-export function replLoop(): void {
+export async function replLoop(): Promise<void> {
   window.deno = deno; // FIXME use a new scope (rather than window).
 
   const historyFile = "deno_history.txt";
@@ -58,7 +61,7 @@ export function replLoop(): void {
   let code = "";
   while (true) {
     try {
-      code = readBlock(rid, "> ", "  ");
+      code = await readBlock(rid, "> ", "  ");
     } catch (err) {
       if (err.message === "EOF") {
         break;
@@ -91,14 +94,14 @@ function evaluate(code: string): void {
   }
 }
 
-function readBlock(
+async function readBlock(
   rid: number,
   prompt: string,
   continuedPrompt: string
-): string {
+): Promise<string> {
   let code = "";
   do {
-    code += readline(rid, prompt);
+    code += await readline(rid, prompt);
     prompt = continuedPrompt;
   } while (parenthesesAreOpen(code));
   return code;
diff --git a/src/ops.rs b/src/ops.rs
index e08e677059..f8e3c9dc1c 100644
--- a/src/ops.rs
+++ b/src/ops.rs
@@ -1121,7 +1121,7 @@ fn op_repl_readline(
   // Ignore this clippy warning until this issue is addressed:
   // https://github.com/rust-lang-nursery/rust-clippy/issues/1684
   #[cfg_attr(feature = "cargo-clippy", allow(redundant_closure_call))]
-  Box::new(futures::future::result((move || {
+  blocking!(base.sync(), || -> OpResult {
     let line = resources::readline(rid, &prompt)?;
 
     let builder = &mut FlatBufferBuilder::new();
@@ -1141,7 +1141,7 @@ fn op_repl_readline(
         ..Default::default()
       },
     ))
-  })()))
+  })
 }
 
 fn op_truncate(
diff --git a/tools/repl_test.py b/tools/repl_test.py
index db51ec511b..9969e9804c 100644
--- a/tools/repl_test.py
+++ b/tools/repl_test.py
@@ -86,6 +86,19 @@ class Repl(object):
         assertEqual(err, '')
         assertEqual(code, 0)
 
+    def test_set_timeout(self):
+        # Special treatment
+        p = Popen([self.deno_exe], stdout=PIPE, stderr=PIPE, stdin=PIPE)
+        # Print after 0.1 second
+        p.stdin.write(
+            "setTimeout(() => console.log('HI'), 100)\n".encode("utf-8"))
+        sleep(0.2)  # Wait 0.2 second before proceed
+        out, err = p.communicate()
+        code = p.poll()
+        assertEqual(out.replace('\r\n', '\n'), '1\nHI\n')
+        assertEqual(err.replace('\r\n', '\n'), '')
+        assertEqual(code, 0)
+
     def test_exit_command(self):
         out, err, code = self.input(".exit", "'ignored'", exit=False)
         assertEqual(out, '')