diff --git a/src/pymatgen/util/io_utils.py b/src/pymatgen/util/io_utils.py
index 7bf4efdc2f4..f8c7d268f43 100644
--- a/src/pymatgen/util/io_utils.py
+++ b/src/pymatgen/util/io_utils.py
@@ -81,7 +81,7 @@ def micro_pyawk(filename, search, results=None, debug=None, postdebug=None):
     for entry in search:
         entry[0] = re.compile(entry[0])
 
-    with zopen(filename, mode="rt", encoding="utf-8") as file:
+    with zopen(filename, mode="rt") as file:
         for line in file:
             for entry in search:
                 match = re.search(entry[0], line)
diff --git a/tests/io/pwmat/test_inputs.py b/tests/io/pwmat/test_inputs.py
index e1438482623..2f2cd60ac93 100644
--- a/tests/io/pwmat/test_inputs.py
+++ b/tests/io/pwmat/test_inputs.py
@@ -47,7 +47,7 @@ class TestACstrExtractor(PymatgenTest):
     def test_extract(self):
         filepath = f"{TEST_DIR}/atom.config"
         ac_extractor = ACExtractor(file_path=filepath)
-        with zopen(filepath, mode="rt", encoding="utf-8") as file:
+        with zopen(filepath, mode="rt") as file:
             ac_str_extractor = ACstrExtractor(atom_config_str="".join(file.readlines()))
         assert ac_extractor.n_atoms == ac_str_extractor.get_n_atoms()
         for idx in range(9):