diff --git a/src/include/rust.hh b/src/include/rust.hh
index c7f3fd9..baa2fbc 100644
--- a/src/include/rust.hh
+++ b/src/include/rust.hh
@@ -11,20 +11,22 @@
 
 type Cstr = char *;
 
-/** The main function: does main things */
-fn rustpp__main () -> i32;
 
 mod termination {
-    class Termination {
+    struct ExitCode {
+        int code;
         fn return_value () -> int {
-            return 0;
+            return code;
         }
     };
 }
 
+/** The main function: does main things */
+fn rustpp__main () -> termination::ExitCode;
+
 mod option {
     template <typename T>
-    class Option: termination::Termination {
+    class Option {
         union {
             u8 None = 0;
             T Some;
@@ -37,6 +39,10 @@ mod option {
        public:
         makeSelf (Option<T>);
 
+        operator termination::ExitCode () {
+            return { (int) variant };
+        }
+
         static fn Some (T value) -> Self {
             Self op;
             op.value.Some = value;
@@ -51,10 +57,6 @@ mod option {
             return op;
         }
 
-        fn return_value () -> int {
-            return self.is_some ();
-        }
-
         fn is_some () -> bool {
             return variant == variant::Some;
         }
@@ -117,6 +119,10 @@ mod result {
        public:
         makeSelf (Result<T, E>);
 
+        operator termination::ExitCode () {
+            return { (int) variant };
+        }
+
         // TODO: destructor for Result
 
         static fn Ok (T value) -> Self {
@@ -372,7 +378,8 @@ mod env {
 mod prelude {
     use slice::Slice;
     use option::Option, option::Some, option::None;
-    use result::Result;
+    use result::Result, result::Err, result::Ok;
+    use termination::ExitCode;
 }
 
 
diff --git a/src/main.cc b/src/main.cc
index 0ab0454..aedb934 100644
--- a/src/main.cc
+++ b/src/main.cc
@@ -3,7 +3,7 @@
 // rust.hh changes language semantics, so must be included last!
 #include "rust.hh"
 
-fn main () -> i32 {
+fn main () -> ExitCode {
     let v = vec::Vec<i32>::new ();
 
     v.push (10);
@@ -21,5 +21,5 @@ fn main () -> i32 {
         std::println ("{}", x);
     }
 
-    return 0;
+    return Err<int, const char *> ("Oops!");
 }
diff --git a/src/runtime.cc b/src/runtime.cc
index 7da472b..a6cfcb7 100644
--- a/src/runtime.cc
+++ b/src/runtime.cc
@@ -11,12 +11,15 @@ namespace {
 }
 
 fn main (int argc, char **argv) -> int {
+    int exitcode = 0;
     program_args = { (Cstr *) argv, (usize) argc };
     try {
-        return rustpp__main ();
+        exitcode = rustpp__main ().return_value ();
     } catch (panic::Panic p) {
         std::println ("Thread exited with explicit panic: {}", p.what ());
+        exitcode = -1;
     }
+    return exitcode;
 }
 
 // Environment