diff --git a/classes/resilient/book.lua b/classes/resilient/book.lua
index b3df075..59de7c7 100644
--- a/classes/resilient/book.lua
+++ b/classes/resilient/book.lua
@@ -306,6 +306,14 @@ function class:registerStyles ()
                       reference = "sectioning-other-number",
                     } },
   })
+  self:registerStyle("sectioning-appendix", { inherit = "sectioning-chapter" }, {
+    sectioning = { numberstyle= {
+                      main = "sectioning-appendix-main-number",
+                      header = "sectioning-appendix-head-number",
+                      reference = "sectioning-appendix-ref-number",
+                    },
+                  },
+  })
 
   self:registerStyle("sectioning-part-base-number", {}, {
     numbering = { display = "ROMAN" }
@@ -322,6 +330,7 @@ function class:registerStyles ()
   self:registerStyle("sectioning-part-ref-number", { inherit = "sectioning-part-base-number" }, {
     numbering = { before = { text ="part " } },
   })
+
   self:registerStyle("sectioning-chapter-base-number", {}, {
   })
   self:registerStyle("sectioning-chapter-main-number", { inherit = "sectioning-chapter-base-number" }, {
@@ -337,6 +346,17 @@ function class:registerStyles ()
     numbering = { before = { text ="chap. " } },
   })
 
+  self:registerStyle("sectioning-appendix-main-number", { inherit = "sectioning-chapter-main-number" }, {
+    numbering = { before = { text = "Appendix "},
+                  display = "ALPHA",
+                },
+  })
+  self:registerStyle("sectioning-appendix-head-number", { inherit = "sectioning-chapter-head-number" }, {
+  })
+  self:registerStyle("sectioning-appendix-ref-number", { inherit = "sectioning-chapter-ref-number" }, {
+    numbering = { before = { text ="app. " } },
+  })
+
   self:registerStyle("sectioning-other-number", {}, {
     numbering = { after = { text = ".", kern = "iwsp" } }
   })
@@ -673,6 +693,17 @@ function class:registerCommands ()
     end
   end, "Applies section hooks (footers and headers, etc.)")
 
+  self:registerCommand("appendix", function (options, content)
+    if self.resilientState.appendix then
+      SU.error("Already in the \\appendix sub-division")
+    end
+    if self.resilientState.division and self.resilientState.division < 2 then
+      SU.error("\\appendix is not valid in " .. DIVISIONNAME[self.resilientState.division])
+    end
+    self.resilientState.appendix = true
+    SILE.call("set-multilevel-counter", { id = "sections", level = 1, value = 0 })
+  end, "Switch to appendix sub-division.")
+
   self:registerCommand("part", function (options, content)
     if self.resilientState.division and self.resilientState.division ~= 2 then
       options.numbering = false
@@ -682,10 +713,10 @@ function class:registerCommands ()
   end, "Begin a new part.")
 
   self:registerCommand("chapter", function (options, content)
-    if self.resilientState.division and self.resilientState.division ~= 2 then
+    if not self.resilientState.appendix and self.resilientState.division and self.resilientState.division ~= 2 then
       options.numbering = false
     end
-    options.style = "sectioning-chapter"
+    options.style = self.resilientState.appendix and "sectioning-appendix" or "sectioning-chapter"
     SILE.call("sectioning", options, content)
   end, "Begin a new chapter.")
 
diff --git a/examples/manual-classes/classes.sil b/examples/manual-classes/classes.sil
index 427bc11..a61b6c7 100644
--- a/examples/manual-classes/classes.sil
+++ b/examples/manual-classes/classes.sil
@@ -314,7 +314,7 @@ The environment relies on the same-named style for its styling and on the
 \autodoc:setting{book.blockquote.margin} setting for its indentation (defaults to 2em). Indented
 quotes can be nested.
 
-\section{Front, main and back divisions}
+\section{Additional book divisions}
 
 The class supports the standard \autodoc:command{\frontmatter}, \autodoc:command{\mainmatter} and \autodoc:command{\backmatter} commands to switch between the different higher-level divisions of the document.
 Obviously, these commands can only occur once in the document, and in the order given above.
@@ -342,10 +342,16 @@ They start a new page, and influence the style of folios.
   \caption{Styles used for folios in different document divisions.}
 \end{table}
 
-Books not using these divisions assume "main" matter by default.
-In the "front" and "back" matter divisions, parts and chapters are never numbered.
+Books not using these divisions assume “main” matter by default.
+In the “front” and “back” matter divisions, parts and chapters are never numbered.
 Not that this is not a configurable style decision, but the very definition of these divisions.
-In "main" matter, they are numbered by default, although this can be changed either on the sectioning command itself, or globally with adequate styles.
+In the main matter, they are numbered by default, although this can be changed either on the sectioning command itself, or globally with adequate styles.
+
+The class also supports the \autodoc:command{\appendix} command, which can only be invoke once, either in the main matter or in the back matter.
+After that, the chapter counter is reset and chapters now use appendix sectioning styles.
+By default, these styles derive from the chapter styles, with the numbering changed to uppercase letters, and the prefix text to “Appendix”.
+Note that appendices are numbered even in the back matter, by default, according to common practice.
+Again, this can be changed on the sectioning command itself, or globally with adequate styles.
 
 \section{Other features}
 
diff --git a/examples/manual-styling/basics/sectioning.md b/examples/manual-styling/basics/sectioning.md
index ea66c66..00caef9 100644
--- a/examples/manual-styling/basics/sectioning.md
+++ b/examples/manual-styling/basics/sectioning.md
@@ -75,6 +75,8 @@ numbering in the table of contents is handled with a different mechanism,
 as a part of the ToC styles. Whether there is a need to reconcile these
 solutions might be considered in a future revision.]
 Note that if a given context is absent, the section number will not be displayed.
+This might be sufficient to disable inherited numbering in some contexts, but
+in these cases, you can just set the `main` number style to `null` (without quotes).
 
 For the "main" number style, some sections may expect the number to be on its
 own standalone line rather than just before the section title.—Chapters and parts,
diff --git a/examples/sile-resilient-manual-styles.yml b/examples/sile-resilient-manual-styles.yml
index 61bf432..bf98f72 100644
--- a/examples/sile-resilient-manual-styles.yml
+++ b/examples/sile-resilient-manual-styles.yml
@@ -697,6 +697,38 @@ prosody:
       before:
         skip: "smallskip"
 
+sectioning-appendix:
+  inherit: "sectioning-chapter"
+  origin: "resilient.book"
+  style:
+    sectioning:
+      numberstyle:
+        header: "sectioning-appendix-head-number"
+        main: "sectioning-appendix-main-number"
+        reference: "sectioning-appendix-ref-number"
+
+sectioning-appendix-head-number:
+  inherit: "sectioning-chapter-head-number"
+  origin: "resilient.book"
+  style:
+
+sectioning-appendix-main-number:
+  inherit: "sectioning-chapter-main-number"
+  origin: "resilient.book"
+  style:
+    numbering:
+      before:
+        text: "Appendix "
+      display: "ALPHA"
+
+sectioning-appendix-ref-number:
+  inherit: "sectioning-chapter-ref-number"
+  origin: "resilient.book"
+  style:
+    numbering:
+      before:
+        text: "app. "
+
 sectioning-base:
   origin: "resilient.book"
   style:
diff --git a/packages/resilient/sectioning/init.lua b/packages/resilient/sectioning/init.lua
index fbce6ad..0fc51c8 100644
--- a/packages/resilient/sectioning/init.lua
+++ b/packages/resilient/sectioning/init.lua
@@ -36,6 +36,21 @@ local function hasContent()
   return hasNonGlueContent
 end
 
+local function nameIfNotNull (name)
+  -- Nothig to fancy but there's a special case for the null value in YAML
+  -- style definitions.
+  if not name then
+    return nil
+  end
+  if type(name) == "string" then
+    return name
+  end
+  if tostring(name) == "yaml.null" then
+    return nil
+  end
+  SU.error("Invalid style name, expected a string or YAML null")
+end
+
 function package:registerCommands ()
 
   local resolveSectionStyleDef = function (name)
@@ -99,7 +114,8 @@ function package:registerCommands ()
     -- shouldn't trigger a goodbreak in-between).
 
     -- Process the section (title) content
-    local numSty = secStyle.numberstyle.main and self:resolveStyle(secStyle.numberstyle.main)
+    local numStyName = secStyle.numberstyle.main and nameIfNotNull(secStyle.numberstyle.main)
+    local numSty = numStyName and self:resolveStyle(numStyName)
     local numDisplay = numSty and numSty.numbering and numSty.numbering.display or "arabic"
 
     -- Counter for numbered sections
@@ -124,8 +140,11 @@ function package:registerCommands ()
       hookOptions.counter = secStyle.counter.id
       hookOptions.level = secStyle.counter.level
       hookOptions.before = true -- HACK SEE BELOW
-      local numsty = sty.sectioning and sty.sectioning.numberstyle
-          and sty.sectioning.numberstyle.header
+      local numsty = sty.sectioning
+          and sty.sectioning.numberstyle
+          -- Only user header number if main number style is defined
+          and nameIfNotNull(sty.sectioning.numberstyle.main)
+          and nameIfNotNull(sty.sectioning.numberstyle.header)
       if numbering and numsty then
         titleHookContent = {
           createCommand("style:apply:number", { name = numsty, text = number }),
@@ -176,9 +195,9 @@ function package:registerCommands ()
 
     -- Show section number (if numbering is true AND a main style is defined)
     if numbering then
-      if secStyle.numberstyle.main then
+      if numStyName then
         titleContent[#titleContent + 1] =
-          createCommand("style:apply:number", { name = secStyle.numberstyle.main, text = number })
+          createCommand("style:apply:number", { name = numStyName, text = number })
         if SU.boolean(numSty.numbering and numSty.numbering.standalone, false) then
           titleContent[#titleContent + 1] =
             createCommand("hardbreak")