tabs are verboten.
diff --git a/Doc/documenting/style.rst b/Doc/documenting/style.rst
index d055711..9baab12 100644
--- a/Doc/documenting/style.rst
+++ b/Doc/documenting/style.rst
@@ -14,9 +14,10 @@
Use of whitespace
-----------------
-All reST files use an indentation of 3 spaces. The maximum line length is 80
-characters for normal text, but tables, deeply indented code samples and long
-links may extend beyond that.
+All reST files use an indentation of 3 spaces; no tabs are allowed. The
+maximum line length is 80 characters for normal text, but tables, deeply
+indented code samples and long links may extend beyond that. Code example
+bodies should use normal Python 4-space indentation.
Make generous use of blank lines where applicable; they help grouping things
together.