diff --git a/ffi_util/ffi_util.mbti b/ffi_util/ffi_util.mbti
new file mode 100644
index 000000000..51ac09400
--- /dev/null
+++ b/ffi_util/ffi_util.mbti
@@ -0,0 +1,11 @@
+package moonbitlang/core/ffi_util
+
+// Values
+
+// Types and methods
+pub type RawFunction
+
+// Type aliases
+
+// Traits
+
diff --git a/ffi_util/moon.pkg.json b/ffi_util/moon.pkg.json
new file mode 100644
index 000000000..0967ef424
--- /dev/null
+++ b/ffi_util/moon.pkg.json
@@ -0,0 +1 @@
+{}
diff --git a/ffi_util/raw_function.mbt b/ffi_util/raw_function.mbt
new file mode 100644
index 000000000..34939490b
--- /dev/null
+++ b/ffi_util/raw_function.mbt
@@ -0,0 +1,4 @@
+/// A compiler builtin type for raw functions, i.e. functions without any capture.
+/// This is useful when passing callbacks to FFI.
+/// Here `T` must be a function type in `RawFunction[T]`
+pub type RawFunction[T]