diff --git a/documentation/content/en/books/porters-handbook/slow-porting/chapter.adoc b/documentation/content/en/books/porters-handbook/slow-porting/chapter.adoc
--- a/documentation/content/en/books/porters-handbook/slow-porting/chapter.adoc
+++ b/documentation/content/en/books/porters-handbook/slow-porting/chapter.adoc
@@ -132,6 +132,7 @@
 ====
 
 Patches are saved into files named [.filename]#patch-*# where * indicates the pathname of the file that is patched, such as [.filename]#patch-Imakefile# or [.filename]#patch-src-config.h#.
+Patches with file names which do not start with [.filename]#patch-# will not be applied automatically.
 
 After the file has been modified, man:diff[1] is used to record the differences between the original and the modified version. `-u` causes man:diff[1] to produce "unified" diffs, the preferred form.
 
@@ -210,6 +211,10 @@
 === Patching Conditionally
 
 Some ports need patches that are only applied for specific FreeBSD versions or when a particular option is enabled or disabled. Conditional patches are specified by placing the full paths to the patch files in `EXTRA_PATCHES`.
+Conditional patch file names usually start with [.filename]#extra-# although
+this is not necessary.  However their file names _must not_ start with
+[.filename]#patch-#.  If they do, they will be first applied unconditionally by
+the framework which is not what you want.
 
 [[slow-patch-extra-ex1]]
 .Applying a Patch for a Specific FreeBSD Version