diff --git a/fmf/utils.py b/fmf/utils.py
index 7bc13faf..2d69ad31 100644
--- a/fmf/utils.py
+++ b/fmf/utils.py
@@ -11,9 +11,10 @@
 import sys
 import time
 import warnings
+from collections.abc import Iterable
 from io import StringIO
 # TODO: py3.10: typing.Optional, typing.Union -> '|' operator
-from typing import Any, NamedTuple, Optional
+from typing import Any, NamedTuple, Optional, Union
 
 from filelock import FileLock, Timeout
 from ruamel.yaml import YAML, scalarstring
@@ -118,7 +119,11 @@ def pluralize(singular=None):
     return plural
 
 
-def listed(items, singular=None, plural=None, max=None, quote="", join="and"):
+def listed(items: Union[int, Iterable[int]],
+           singular: Optional[str] = None,
+           plural: Optional[str] = None,
+           max: Optional[str] = None,
+           quote: str = "", join: str = "and") -> str:
     """
     Convert an iterable into a nice, human readable list or description::
 
@@ -189,7 +194,7 @@ def split(values, separator=re.compile("[ ,]+")):
     return sum([separator.split(value) for value in values], [])
 
 
-def info(message, newline=True):
+def info(message: str, newline: bool = True) -> None:
     """ Log provided info message to the standard error output """
     sys.stderr.write(message + ("\n" if newline else ""))
 
@@ -454,7 +459,9 @@ def get(self):
 #  Coloring
 # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-def color(text, color=None, background=None, light=False, enabled="auto"):
+def color(text: str, color: Optional[str] = None,
+          background: Optional[str] = None,
+          light: Optional[str] = False, enabled: str = "auto"):
     """
     Return text in desired color if coloring enabled
 
@@ -553,7 +560,7 @@ def enabled(self):
 #  Cache directory
 # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-def get_cache_directory(create=True):
+def get_cache_directory(create: bool = True) -> str:
     """
     Return cache directory, created by this call if necessary
 
@@ -593,7 +600,7 @@ def set_cache_expiration(seconds):
     CACHE_EXPIRATION = int(seconds)
 
 
-def clean_cache_directory():
+def clean_cache_directory() -> None:
     """ Delete used cache directory if it exists """
     cache = get_cache_directory(create=False)
     if os.path.isdir(cache):