diff --git a/cd/__init__.py b/cd/__init__.py
index a5d1bb8..da2943e 100644
--- a/cd/__init__.py
+++ b/cd/__init__.py
@@ -12,11 +12,11 @@ projects = Projects(os.environ)
 project = Project(projects)
 
 
-def cd_browse_workspace():
+def cd_browse_workspace() -> None:
     browse(project.root)
 
 
-def cd_build_project():
+def cd_build_project() -> None:
     for extension in ["py", "sh"]:
         path = os.path.join(project.root, f"build.{extension}")
         if os.path.exists(path):
@@ -26,7 +26,7 @@ def cd_build_project():
         pass
 
 
-def cd_clone_branch():
+def cd_clone_branch() -> None:
     print(f"""\
 {project.url}
 ↓
@@ -40,12 +40,12 @@ def cd_clone_branch():
     )
 
 
-def cd_list_environment():
+def cd_list_environment() -> None:
     for variable, value in sorted(projects.environment.items()):
         print(variable, "=", value)
 
 
-def cd_synchronize():
+def cd_synchronize() -> None:
     host = "rwx.work"
     source = "out"
     user = "cd"
@@ -64,7 +64,7 @@ def cd_synchronize():
     )
 
 
-def browse(root: str):
+def browse(root: str) -> None:
     paths = []
     for directory, _, files in os.walk(root):
         for file in files:
@@ -77,13 +77,13 @@ def browse(root: str):
     shut(root)
 
 
-def cat(file: str):
+def cat(file: str) -> None:
     open(file)
     print(fs.read_file_text(file).rstrip())
     shut(file)
 
 
-def install_commands(path):
+def install_commands(path) -> None:
     step("Install commands")
     user = "/usr/local/bin"
     for command in [
@@ -97,7 +97,7 @@ def install_commands(path):
         os.symlink(path, os.path.join(user, f"{COMMANDS_PREFIX}{command}"))
 
 
-def set_ssh(*arguments):
+def set_ssh(*arguments) -> None:
     step("Set SSH")
     #
     ssh_key, ssh_hosts = arguments
@@ -124,21 +124,21 @@ def set_ssh(*arguments):
     cat(known)
 
 
-def open(*arguments):
+def open(*arguments) -> None:
     print(env.CD_OPEN, end="")
     print(*arguments, flush=True)
 
 
-def shut(*arguments):
+def shut(*arguments) -> None:
     print(env.CD_SHUT, end="")
     print(*arguments, flush=True)
 
 
-def split():
+def split() -> None:
     print(env.CD_SPLT, flush=True)
 
 
-def step(*arguments):
+def step(*arguments) -> None:
     env.CD_STEP += 1
     print(env.CD_DOWN)
     print(env.CD_VERT, env.CD_STEP, *arguments)