--- buffer.c.~1.583.~	2009-07-17 21:12:21.000000000 +0200
+++ buffer.c	2009-07-22 03:55:26.000000000 +0200
@@ -5727,7 +5727,9 @@
 
   DEFVAR_PER_BUFFER ("case-fold-search", &current_buffer->case_fold_search,
 		     Qnil,
-		     doc: /* *Non-nil if searches and matches should ignore case.  */);
+		     doc: /* *Non-nil if searches and matches should ignore case.
+If there is an uppercase character in the search string
+then the search becomes case sensitive.  */);
 
   DEFVAR_PER_BUFFER ("fill-column", &current_buffer->fill_column,
 		     make_number (Lisp_Int),