diff --git a/CODING_CONVENTIONS.md b/CODING_CONVENTIONS.md
index f39db60f6e..f6adb3da2d 100644
--- a/CODING_CONVENTIONS.md
+++ b/CODING_CONVENTIONS.md
@@ -97,7 +97,7 @@
 
 ## Return values
 
-* Any function must return one of the following values:
+* Every function must return one of the following values or none (void):
     * logical value (zero or not zero)
     * an error code (given as a negative number or zero) or a positive status
       value