diff --git a/docs/reference/constrained.rst b/docs/reference/constrained.rst
index 8b64fd98fc..2bcf9f7fb7 100644
--- a/docs/reference/constrained.rst
+++ b/docs/reference/constrained.rst
@@ -392,6 +392,8 @@ Symbol Meaning
    F   float
    B   byte code
    M   module
+   S   string or bytes
+   A   bytearray
 ====== =================
 
 Each letter represents a single block of memory, a block being 16 bytes. So each