diff --git a/itconfig-macro/src/lib.rs b/itconfig-macro/src/lib.rs
index 038de09..edb51a8 100644
--- a/itconfig-macro/src/lib.rs
+++ b/itconfig-macro/src/lib.rs
@@ -1,6 +1,7 @@
 #![recursion_limit = "256"]
 #![deny(clippy::all)]
 #![forbid(unsafe_code)]
+#![forbid(non_ascii_idents)]
 
 mod ast;
 mod expand;
diff --git a/itconfig/src/lib.rs b/itconfig/src/lib.rs
index e0f1dfa..a5ef282 100644
--- a/itconfig/src/lib.rs
+++ b/itconfig/src/lib.rs
@@ -134,6 +134,7 @@
 
 // Rustc lints.
 #![forbid(unsafe_code)]
+#![forbid(non_ascii_idents)]
 #![deny(
     missing_debug_implementations,
     missing_docs,