diff --git a/src/main/wacc/Main.scala b/src/main/wacc/Main.scala
index 8bf7d3b..71a65bb 100644
--- a/src/main/wacc/Main.scala
+++ b/src/main/wacc/Main.scala
@@ -40,26 +40,29 @@ val cliParser = {
 
 def frontend(
     contents: String
-)(using stdout: PrintStream): IO[microWacc.Program] = {
-  IO(parser.parse(contents)).flatMap {
-    case Failure(msg) => IO.raiseError(new RuntimeException(msg))
+)(using stdout: PrintStream): IO[Either[Int, microWacc.Program]] = {
+  IO(parser.parse(contents)).map {
+    case Failure(msg) =>
+      stdout.println(msg)
+      Left(100) // Syntax error
+
     case Success(prog) =>
-    given errors: mutable.Builder[Error, List[Error]] = List.newBuilder
-    given errorContent: String = contents
+      given errors: mutable.Builder[Error, List[Error]] = List.newBuilder
+      given errorContent: String = contents
 
-    val (names, funcs) = renamer.rename(prog)
-    given ctx: typeChecker.TypeCheckerCtx = typeChecker.TypeCheckerCtx(names, funcs, errors)
+      val (names, funcs) = renamer.rename(prog)
+      given ctx: typeChecker.TypeCheckerCtx = typeChecker.TypeCheckerCtx(names, funcs, errors)
 
-    val typedProg = typeChecker.check(prog)
+      val typedProg = typeChecker.check(prog)
 
-    if (errors.result.isEmpty) IO.pure(typedProg)
-    else {
-    errors.result.foreach(printError)
-        IO.raiseError(new RuntimeException("Compilation failed with code: " + errors.result.view.map {
-      case _: Error.InternalError => 201
-      case _                      => 200
-    }.max))
-    }
+      if (errors.result.isEmpty) Right(typedProg)
+      else {
+        errors.result.foreach(printError)
+        Left(errors.result.view.map {
+          case _: Error.InternalError => 201
+          case _                      => 200
+        }.max)
+      }
   }
 }
 
@@ -72,15 +75,19 @@ def compile(filename: String, outFile: Option[File] = None)(using
     stdout: PrintStream = Console.out
 ): IO[Int] =
   for {
-  contents <- IO(os.read(os.Path(filename)))
-  typedProg <- frontend(contents)
-  _ <- IO {
-        writer.writeTo(
-          backend(typedProg),
-          PrintStream(outFile.getOrElse(File(filename.stripSuffix(".wacc") + ".s")))
-        )
-  }
-} yield 0
+    contents <- IO(os.read(os.Path(filename)))
+    result <- frontend(contents)
+    exitCode <- result match {
+      case Left(code) => IO.pure(code) // Return error code
+      case Right(typedProg) =>
+        IO {
+          writer.writeTo(
+            backend(typedProg),
+            PrintStream(outFile.getOrElse(File(filename.stripSuffix(".wacc") + ".s")))
+          )
+        }.as(0) // Compilation succeeded
+    }
+  } yield exitCode
 
 object Main extends IOApp.Simple {
   override def run: IO[Unit] =