diff --git a/pep-3154.txt b/pep-3154.txt
index 9fc3eb135..9d919bf4a 100644
--- a/pep-3154.txt
+++ b/pep-3154.txt
@@ -71,11 +71,14 @@ of a pickle is thus the following::
 
 To keep the implementation simple, it is forbidden for a pickle opcode
 to overlap frame boundaries.  The pickler takes care not to produce such
-pickles, and the unpickler refuses them.
+pickles, and the unpickler refuses them.  Also, there is no "last frame"
+marker.  The last frame is simply the one which ends with a STOP opcode.
 
-How the pickler decides frame sizes is an implementation detail.
-A simple heuristic committing the current frame as soon as it reaches
-64 KiB seems sufficient.
+.. note::
+
+   How the pickler partitions the pickle stream into frames is an
+   implementation detail.  "Closing" a frame as soon as it reaches
+   ~64 KiB should be ok for both performance and pickle size overhead.
 
 Binary encoding for all opcodes
 -------------------------------