1 files changed, 2 insertions, 0 deletions
diff --git a/C-STYLE.md b/C-STYLE.md
index 9a5f298..05dd732 100644
--- a/C-STYLE.md
+++ b/C-STYLE.md
@@ -104,6 +104,8 @@ but merely how to format it.
 
 * Declare functions `static` when they are only used in this translation unit.
 
+* Use lowercase hexadecimal digits.
+
 ## Idioms:
 
 * Using the return value of `=` is ok.