Extend "when necessary" explanation
diff --git a/CppCoreGuidelines.md b/CppCoreGuidelines.md
index 1ae151b02..427b09911 100644
--- a/CppCoreGuidelines.md
+++ b/CppCoreGuidelines.md
@@ -9214,7 +9214,7 @@ The default is the easiest to read and write.
 
 ##### Note
 
-Specifying the underlying type is necessary in forward declarations of enumerations:
+Specifying the underlying type is necessary to forward-declare an enum or enum class:
 
     enum Flags : char;
 
@@ -9224,6 +9224,9 @@ Specifying the underlying type is necessary in forward declarations of enumerati
 
     enum Flags : char { /* ... */ };
 
+or to ensure that values of that type have a specified bit-precision:
+
+    enum Bitboard : uint64_t { /* ... */ };
 
 ##### Enforcement
 

Extend Enum.7 `Note` section for #1977