diff --git a/lib/api/src/externals/function.rs b/lib/api/src/externals/function.rs
index 6b9aa6bef..80305d9dc 100644
--- a/lib/api/src/externals/function.rs
+++ b/lib/api/src/externals/function.rs
@@ -907,6 +907,9 @@ mod inner {
     impl_host_function!([C] S25, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, A16, A17, A18, A19, A20, A21, A22, A23, A24, A25);
     impl_host_function!([C] S26, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, A16, A17, A18, A19, A20, A21, A22, A23, A24, A25, A26);
 
+    // Implement `WasmTypeList` on `Infallible`, which means that
+    // `Infallible` can be used as a returned type of a host function
+    // to express that it doesn't return.
     impl WasmTypeList for Infallible {
         type CStruct = Self;
         type Array = [i128; 0];