diff --git a/alibuild_helpers/cmd.py b/alibuild_helpers/cmd.py
index a0ea2db5..4f411f4a 100644
--- a/alibuild_helpers/cmd.py
+++ b/alibuild_helpers/cmd.py
@@ -54,9 +54,10 @@ def getstatusoutput(command, timeout=None):
   return proc.returncode, merged_output
 
 
-def execute(command, printer=debug, timeout=None):
+def execute(command: str | list[str], printer=debug, timeout:int | None =None) -> int:
   popen = Popen(command, shell=isinstance(command, str), stdout=PIPE, stderr=STDOUT)
   start_time = time.time()
+  assert popen.stdout is not None, "Could not open stdout for command"
   for line in iter(popen.stdout.readline, b""):
     printer("%s", decode_with_fallback(line).strip("\n"))
     if timeout is not None and time.time() > start_time + timeout:
diff --git a/alibuild_helpers/doctor.py b/alibuild_helpers/doctor.py
index 8c0fa42c..8fa29030 100644
--- a/alibuild_helpers/doctor.py
+++ b/alibuild_helpers/doctor.py
@@ -7,7 +7,7 @@
 from alibuild_helpers.utilities import getPackageList, parseDefaults, readDefaults, validateDefaults
 from alibuild_helpers.cmd import getstatusoutput, DockerRunner
 
-def prunePaths(workDir):
+def prunePaths(workDir: str) -> None:
   for x in ["PATH", "LD_LIBRARY_PATH", "DYLD_LIBRARY_PATH"]:
     if not x in os.environ:
       continue
@@ -52,7 +52,7 @@ def checkRequirements(spec, cmd, homebrew_replacement, getstatusoutput_docker):
           spec.get("system_requirement_missing"))
     return (err, "")
 
-def systemInfo():
+def systemInfo() -> None:
   _,out = getstatusoutput("env")
   debug("Environment:\n%s", out)
   _,out = getstatusoutput("uname -a")
diff --git a/alibuild_helpers/init.py b/alibuild_helpers/init.py
index ad93b116..5016baf4 100644
--- a/alibuild_helpers/init.py
+++ b/alibuild_helpers/init.py
@@ -8,7 +8,7 @@
 import os.path as path
 import os, sys
 
-def parsePackagesDefinition(pkgname):
+def parsePackagesDefinition(pkgname: str):
   return [ dict(zip(["name","ver"], y.split("@")[0:2]))
            for y in [ x+"@" for x in list(filter(lambda y: y, pkgname.split(","))) ] ]