diff --git a/src/basic/missing_audit.h b/src/basic/missing_audit.h
index 96248bc9d8c..3f72acf02f6 100644
--- a/src/basic/missing_audit.h
+++ b/src/basic/missing_audit.h
@@ -25,6 +25,8 @@ assert_cc(AUDIT_SERVICE_STOP == 1131);
 assert_cc(MAX_AUDIT_MESSAGE_LENGTH == 8970);
 #endif
 
+/* Note: we check for AUDIT_NLGRP_MAX because it's a define, but we actually
+ * need AUDIT_NLGRP_READLOG which is an enum. */
 #ifndef AUDIT_NLGRP_MAX
 #  define AUDIT_NLGRP_READLOG 1
 #else