diff --git a/src/Zir.zig b/src/Zir.zig
index 8b65fd1c6..3f19dd3e0 100644
--- a/src/Zir.zig
+++ b/src/Zir.zig
@@ -2387,13 +2387,16 @@ pub const Inst = struct {
     ///        link_section: Ref, // if corresponding bit is set
     ///    }
     /// 2. inst: Index // for every body_len
-    /// 3. has_bits: u32 // for every 16 fields
-    ///    - sets of 2 bits:
-    ///      0b0X: whether corresponding field has an align expression
-    ///      0bX0: whether corresponding field has a default expression
+    /// 3. has_bits: u32 // for every 8 fields
+    ///    - sets of 4 bits:
+    ///      0b000X: whether corresponding field has an align expression
+    ///      0b00X0: whether corresponding field has a default expression
+    ///      0b0X00: whether corresponding field is comptime
+    ///      0bX000: unused
     /// 4. fields: { // for every fields_len
     ///        field_name: u32,
     ///        field_type: Ref,
+    ///        - if none, means `anytype`.
     ///        align: Ref, // if corresponding bit is set
     ///        default_value: Ref, // if corresponding bit is set
     ///    }