diff --git a/poky/documentation/sphinx/yocto-vars.py b/poky/documentation/sphinx/yocto-vars.py
index 8083d7d..8795eee 100644
--- a/poky/documentation/sphinx/yocto-vars.py
+++ b/poky/documentation/sphinx/yocto-vars.py
@@ -1,4 +1,6 @@
 #!/usr/bin/env python
+from hashlib import md5
+from pathlib import Path
 import re
 import sys
 
@@ -20,25 +22,62 @@
 # Each .rst file is processed after source-read event (subst_vars_replace runs once per file)
 subst_vars = {}
 
+poky_hash = ""
+
 def subst_vars_replace(app: Sphinx, docname, source):
     result = source[0]
     for k in subst_vars:
         result = result.replace("&"+k+";", subst_vars[k])
     source[0] = result
 
+def yocto_vars_env_get_outdated(app: Sphinx, env, added, changed, removed):
+    '''
+    If poky.yaml changed (BUILDDIR/.poky.yaml.cache does not exist or contains
+    an md5sum different from poky.yaml's current md5sum), force rebuild of all
+    *.rst files in SOURCEDIR whose content has at least one occurence of `&.*;`
+    (see PATTERN global variable).
+    '''
+    try:
+        poky_cache = Path(app.outdir) / ".poky.yaml.cache"
+        cache_hash = poky_cache.read_text()
+    except FileNotFoundError:
+        cache_hash = None
+
+    if poky_hash == cache_hash:
+        return []
+
+    docs = []
+    for p in Path(app.srcdir).rglob("*.rst"):
+        if PATTERN.search(p.read_text()):
+            p_rel_no_ext = p.relative_to(app.srcdir).parent / p.stem
+            docs.append(str(p_rel_no_ext))
+    return docs
+
+def yocto_vars_build_finished(app: Sphinx, exception):
+    poky_cache = Path(app.outdir) / ".poky.yaml.cache"
+    poky_cache.write_text(poky_hash)
+    return []
+
 PATTERN = re.compile(r'&(.*?);')
 def expand(val, src):
     return PATTERN.sub(lambda m: expand(src.get(m.group(1), ''), src), val)
 
 def setup(app: Sphinx):
-    #FIXME: if poky.yaml changes, files are not reprocessed.
+    global poky_hash
+
     with open("poky.yaml") as file:
-        subst_vars.update(yaml.load(file, Loader=yaml.FullLoader))
+        hasher = md5()
+        buff = file.read()
+        hasher.update(buff.encode('utf-8'))
+        poky_hash = hasher.hexdigest()
+        subst_vars.update(yaml.safe_load(buff))
 
     for k in subst_vars:
         subst_vars[k] = expand(subst_vars[k], subst_vars)
 
     app.connect('source-read', subst_vars_replace)
+    app.connect('env-get-outdated', yocto_vars_env_get_outdated)
+    app.connect('build-finished', yocto_vars_build_finished)
 
     return dict(
         version = __version__,