diff --git a/src/icartt/dataset.py b/src/icartt/dataset.py
index 660a2e9dfb5d218af8ca718116777d960ba88a8a..1528158734013c22172b05a39313f1faaddb41f6 100644
--- a/src/icartt/dataset.py
+++ b/src/icartt/dataset.py
@@ -348,7 +348,7 @@ class Variable:
         # Uppercase and lowercase ASCII alphanumeric characters
         # and underscores.
 
-        allAreAlphaOrUnderscore = all(utl.isAsciiAlphaOrUnderscore(x) for x in name)
+        allAreAlphaOrUnderscore = all(re.match("[a-zA-Z0-9_]", c) for c in name)
         # The first character must be a letter,
         firstIsAlpha = bool(re.match("[a-zA-Z]", name[0]))
         # and the name can be at most 31 characters in length.
@@ -757,7 +757,7 @@ class Dataset:
         :return: is file name valid according to ICARTT standard?
         :rtype: bool
         """
-        allAsciiAlpha = utl.isAsciiAlpha(name)
+        allAsciiAlpha = all(re.match("[a-zA-Z0-9-_.]", c) for c in name)
         lessThan128Characters = len(name) < 128
 
         return allAsciiAlpha and lessThan128Characters and name.endswith(".ict")
diff --git a/src/icartt/ictutils.py b/src/icartt/ictutils.py
index 0f2066c72f2967922994143a415a2eba946467bc..f7f666c4fbfadf0d687261a167a30bbc81ed12b5 100644
--- a/src/icartt/ictutils.py
+++ b/src/icartt/ictutils.py
@@ -1,7 +1,5 @@
 # -*- coding: utf-8 -*-
 
-import re
-
 
 class FilehandleWithLinecounter:
     """a file handle that counts the number of files that were read"""
@@ -19,16 +17,6 @@ class FilehandleWithLinecounter:
         return dmp
 
 
-def isAsciiAlphaOrUnderscore(x: str) -> bool:
-    """check if string x contains only characters from [a-zA-Z0-9_] regex"""
-    return re.match("[a-zA-Z0-9_]", x)
-
-
-def isAsciiAlpha(x):
-    """check if string x contains only characters from [a-zA-Z0-9-_.] regex"""
-    return re.match("[a-zA-Z0-9-_.]", x)
-
-
 def extractVardesc(line_parts: list) -> str:
     """extract variable description from ict header line parts (splitted line)"""
     shortname, units, standardname, longname, *_ = line_parts + [None] * 3