diff --git a/doc/lispref/customize.texi b/doc/lispref/customize.texi
index 6c7ca260ab..7fea507fd0 100644
--- a/doc/lispref/customize.texi
+++ b/doc/lispref/customize.texi
@@ -1432,7 +1432,9 @@ Custom Themes
 would be evaluated when loading the theme, but that is bad form.
 To protect against loading themes containing malicious code, Emacs
 displays the source file and asks for confirmation from the user
-before loading any non-built-in theme for the first time.
+before loading any non-built-in theme for the first time.  As
+such, themes are not ordinarily byte-compiled, and source files
+always take precedence when Emacs is looking for a theme to load.
 
   The following functions are useful for programmatically enabling and
 disabling themes: