diff --git a/Include/internal/pycore_obmalloc.h b/Include/internal/pycore_obmalloc.h
index d4dbe541e6da51..f6b4bd90a23455 100644
--- a/Include/internal/pycore_obmalloc.h
+++ b/Include/internal/pycore_obmalloc.h
@@ -14,6 +14,12 @@ typedef unsigned int pymem_uint;  /* assuming >= 16 bits */
 #undef  uint
 #define uint pymem_uint
 
+/* NOTE: the following overviews were in the initial checkin, in 1998. In
+ * 2026, they're still helpful, but some details have changed. For example,
+ * we now use 32 size classes 16 bytes apart, and an arena is generally at
+ * least 1MB. Use sys._debugmallocstats() to see exact current details for
+ * the specific version of CPython used.
+ */
 
 /* An object allocator for Python.