--- a/doc/manual.docbook.sgml	Sun Sep 19 10:41:17 2010 -0600
+++ b/doc/manual.docbook.sgml	Sun Sep 19 12:04:12 2010 -0600
@@ -405,6 +405,13 @@
 If applicable, the operand follows separated by whitespace. Following the
 opcode and operand is an optional comment.
 </para>
+
+<para> It is important to note that operands cannot contain any whitespace
+except in the case of delimited strings.  This is because the first
+whitespace character will be interpreted as the separator between the
+operand column and the comment.  This behaviour is required for approximate
+source compatibility with other 6x09 assemblers.  </para>
+
 <para>
 A comment can also be introduced with a * or a ;. The comment character is
 optional for end of statement comments. However, if a symbol is the only