diff --git a/tdoc/common/__init__.py b/tdoc/common/__init__.py
index 65b7344..ec675d4 100644
--- a/tdoc/common/__init__.py
+++ b/tdoc/common/__init__.py
@@ -10,7 +10,7 @@
 from sphinx.util import logging
 
 __project__ = 't-doc-common'
-__version__ = '0.7'
+__version__ = '0.8.dev1'
 
 _common = pathlib.Path(__file__).absolute().parent
 _root = _common.parent.parent
@@ -94,6 +94,7 @@ class ExecBlock(nodes.literal_block): pass
 
 class Exec(CodeBlock):
     # TODO: :include:
+    # TODO: Validate the language against the list of supported languages
 
     option_spec = CodeBlock.option_spec | {
         'after': directives.unchanged,
diff --git a/tdoc/common/cli.py b/tdoc/common/cli.py
index d66c953..f876fab 100644
--- a/tdoc/common/cli.py
+++ b/tdoc/common/cli.py
@@ -147,6 +147,7 @@ def __init__(self, *args, cfg, **kwargs):
         self.directory = self.build_dir(0) / 'html'
         self.upgrade_msg = None
         self.stop = False
+        self.building = False
         self.builder = threading.Thread(target=self.watch_and_build)
         self.builder.start()
         self.checker = threading.Thread(target=self.check_upgrade, daemon=True)
@@ -159,14 +160,12 @@ def server_bind(self):
         return super().server_bind()
 
     def finish_request(self, request, client_addr):
-        with self.lock:
-            directory = self.directory
+        with self.lock: directory = self.directory
         self.RequestHandlerClass(request, client_addr, self,
                                  directory=directory)
 
     def server_close(self):
-        with self.lock:
-            self.stop = True
+        with self.lock: self.stop = True
         self.builder.join()
         return super().server_close()
 
@@ -192,8 +191,7 @@ def watch_and_build(self):
                     "\nSource change detected, rebuilding\n")
             prev_mtime = mtime
             if build := self.build(mtime):
-                with self.lock:
-                    self.directory = build / 'html'
+                with self.lock: self.directory = build / 'html'
                 self.print_serving()
                 if build_mtime is not None: self.remove_build_dir(build_mtime)
                 build_mtime = mtime
@@ -223,11 +221,14 @@ def build_dir(self, mtime):
 
     def build(self, mtime):
         build = self.build_dir(mtime)
+        with self.lock: self.building = True
         try:
             res = sphinx_build(self.cfg, 'html', build=build)
             if res.returncode == 0: return build
         except Exception as e:
             self.cfg.stderr.write(f"Build: {e}\n")
+        finally:
+            with self.lock: self.building = False
 
     def remove_build_dir(self, mtime):
         build = self.build_dir(mtime)
@@ -241,8 +242,7 @@ def print_serving(self):
         if ':' in host: host = f'[{host}]'
         self.cfg.stdout.write(self.cfg.ansi("Serving at <@{LBLUE}%s@{NORM}>\n")
                               % f"http://{host}:{port}/")
-        with self.lock:
-            msg = self.upgrade_msg
+        with self.lock: msg = self.upgrade_msg
         if msg: self.cfg.stdout.write(msg)
 
     def check_upgrade(self):
@@ -258,6 +258,7 @@ def check_upgrade(self):
                    'development' if editable else 'install'))
             with self.lock:
                 self.upgrade_msg = msg
+                if not self.building: self.cfg.stdout.write(msg)
         except Exception:
             if self.cfg.debug: raise