diff -aur asn1crypto-1.5.1/dev/_import.py asn1crypto-1.5.1.new/dev/_import.py
--- asn1crypto-1.5.1/dev/_import.py	2022-03-15 15:45:23.000000000 +0100
+++ asn1crypto-1.5.1.new/dev/_import.py	2024-01-07 20:16:55.560811396 +0100
@@ -1,7 +1,9 @@
 # coding: utf-8
 from __future__ import unicode_literals, division, absolute_import, print_function
 
-import imp
+import importlib
+import importlib.machinery
+import importlib.util
 import sys
 import os
 
@@ -34,6 +36,14 @@
         None if not loaded, otherwise the module
     """
 
+    if mod in sys.modules:
+        return sys.modules[mod]
+
+    if mod_dir is None:
+        full_mod = mod
+    else:
+        full_mod = mod_dir
+
     if mod_dir is None:
         mod_dir = mod.replace('.', os.sep)
 
@@ -49,8 +59,16 @@
         path = os.path.join(path, append)
 
     try:
-        mod_info = imp.find_module(mod_dir, [path])
-        return imp.load_module(mod, *mod_info)
+        loader_details = (
+            importlib.machinery.SourceFileLoader,
+            importlib.machinery.SOURCE_SUFFIXES
+        )
+        finder = importlib.machinery.FileFinder(path, loader_details)
+        spec = finder.find_spec(full_mod)
+        module = importlib.util.module_from_spec(spec)
+        sys.modules[mod] = module
+        spec.loader.exec_module(module)
+        return module
     except ImportError:
         if allow_error:
             raise
diff -aur asn1crypto-1.5.1/tests/__init__.py asn1crypto-1.5.1.new/tests/__init__.py
--- asn1crypto-1.5.1/tests/__init__.py	2022-03-15 15:45:23.000000000 +0100
+++ asn1crypto-1.5.1.new/tests/__init__.py	2024-01-07 20:18:32.384639619 +0100
@@ -1,7 +1,10 @@
 # coding: utf-8
 from __future__ import unicode_literals, division, absolute_import, print_function
 
-import imp
+import importlib
+import importlib.machinery
+import importlib.util
+import sys
 import os
 import unittest
 
@@ -28,6 +31,9 @@
         None if not loaded, otherwise the module
     """
 
+    if mod in sys.modules:
+        return sys.modules[mod]
+
     if mod_dir is None:
         mod_dir = mod
 
@@ -38,8 +44,16 @@
         return None
 
     try:
-        mod_info = imp.find_module(mod_dir, [path])
-        return imp.load_module(mod, *mod_info)
+        loader_details = (
+            importlib.machinery.SourceFileLoader,
+            importlib.machinery.SOURCE_SUFFIXES
+        )
+        finder = importlib.machinery.FileFinder(path, loader_details)
+        spec = finder.find_spec(mod_dir)
+        module = importlib.util.module_from_spec(spec)
+        sys.modules[mod] = module
+        spec.loader.exec_module(module)
+        return module
     except ImportError:
         return None