diff --git a/src/tools/tidy/src/fluent_alphabetical.rs b/src/tools/tidy/src/fluent_alphabetical.rs
index 1fadc523591c..769f92d04f0a 100644
--- a/src/tools/tidy/src/fluent_alphabetical.rs
+++ b/src/tools/tidy/src/fluent_alphabetical.rs
@@ -118,5 +118,7 @@ pub fn check(path: &Path, bless: bool, diag_ctx: DiagCtx) {
         },
     );
 
+    assert!(!all_defined_msgs.is_empty());
+
     crate::fluent_used::check(path, all_defined_msgs, diag_ctx);
 }