diff --git a/library/text/encoder/src/html_encoder.e b/library/text/encoder/src/html_encoder.e
index b066c00c..2b63c9ad 100644
--- a/library/text/encoder/src/html_encoder.e
+++ b/library/text/encoder/src/html_encoder.e
@@ -61,7 +61,11 @@ feature -- Encoder
 						Result.extend (c)
 					when '%"' then Result.append_string (""")
 					when '&' then Result.append_string ("&")
-					when '%'' then Result.append_string ("'")
+					when '%'' then Result.append_string ("'")
+						-- The named character reference ' (the apostrophe, U+0027) 
+						-- was introduced in XML 1.0 but does not appear in HTML. 
+						-- Authors should therefore use ' instead of ' 
+						-- to work as expected in HTML 4 user agents.
 					when '<' then Result.append_string ("&lt;")
 					when '>' then Result.append_string ("&gt;")
 					else