diff --git a/runtime/adainclude/unchecked_conversion.ads b/runtime/adainclude/unchecked_conversion.ads
new file mode 100644
index 0000000..0210a54
--- /dev/null
+++ b/runtime/adainclude/unchecked_conversion.ads
@@ -0,0 +1,5 @@
+generic
+   type Source (<>) is limited private;
+   type Target (<>) is limited private;
+function Unchecked_Conversion (S : Source) return Target
+   with Pure, Nonblocking, Import, Convention => Intrinsic;