diff --git a/src/lib.rs b/src/lib.rs
index 86a18a3..67f8b08 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -237,6 +237,9 @@
 )]
 #![cfg_attr(error_generic_member_access, feature(error_generic_member_access))]
 
+#[cfg(all(thiserror_nightly_testing, not(error_generic_member_access)))]
+compile_error!("Build script probe failed to compile.");
+
 mod aserror;
 mod display;
 #[cfg(error_generic_member_access)]