--- ./cppo-1.6.5/src/cppo_eval.ml.old	2019-04-29 18:27:54.177974043 +0100
+++ ./cppo-1.6.5/src/cppo_eval.ml	2019-04-29 18:28:01.770989363 +0100
@@ -85,7 +85,7 @@
 let trim_compact_and_capitalize_string s =
   let buf = Buffer.create (String.length s) in
   trim_and_compact buf s;
-  String.capitalize (Buffer.contents buf)
+  String.capitalize_ascii (Buffer.contents buf)
 
 let is_ident s =
   let len = String.length s in