diff --git a/pyporter/utils.py b/pyporter/utils.py
index 1c8e3d4a833836b30f49f8ac7ab0671160cd7f93..c4456946b1ecc7922a974712ee4a53a579f94818 100644
--- a/pyporter/utils.py
+++ b/pyporter/utils.py
@@ -3,7 +3,12 @@ import re
 
 # TODO: this should be more compatible for https://peps.python.org/pep-0508/
 def transform_module_name(input_str):
-    module_name = re.match(r"([a-zA-Z0-9_-]+)", input_str).group(1).strip()
+    match = re.match(r"([a-zA-Z0-9_-]+)", input_str)
+    if match:
+        module_name = match.group(1).strip()
+    else:
+        raise ValueError("Invalid input format")
+        
     version_names = input_str[len(module_name):].strip().strip("()")
     version_constraint = version_names.split(",")
     package_name = "python3-" + module_name
diff --git a/tests/test_transform_module_name.py b/tests/test_transform_module_name.py
index c292b7d90fadf27593d879e9b4ef4a172ba3a33a..eaefcd64f530dd79b65fce31d6aa9906efbf1ecf 100644
--- a/tests/test_transform_module_name.py
+++ b/tests/test_transform_module_name.py
@@ -16,9 +16,14 @@ class TestTransofrmModuleName(unittest.TestCase):
 
     def test_transform_module_name_strip_whitespace(self):
         input_str = "pyjwkest (>=1.3.6)"
-        expected_output = "(python3-pyjwkest(>=1.3.6))"
+        expected_output = "(python3-pyjwkest>=1.3.6)"
         self.assertEqual(transform_module_name(input_str), expected_output)
 
+    def test_invalid_input(self):
+        input_str = "!invalid_module123"
+        with self.assertRaises(ValueError):
+            transform_module_name(input_str)    
+
 
 if __name__ == '__main__':
     unittest.main()