diff --git a/library/core/src/num/mod.rs b/library/core/src/num/mod.rs
index c2b646b9b3e4a..8ac57528f3e02 100644
--- a/library/core/src/num/mod.rs
+++ b/library/core/src/num/mod.rs
@@ -478,7 +478,7 @@ impl isize {
     }
 }
 
-/// If the 6th bit is set ascii is lower case.
+/// If the bit selected by this mask is set, ascii is lower case.
 const ASCII_CASE_MASK: u8 = 0b0010_0000;
 
 impl u8 {