diff --git a/snirf/pysnirf2.py b/snirf/pysnirf2.py
index ee4db7f..044c81c 100644
--- a/snirf/pysnirf2.py
+++ b/snirf/pysnirf2.py
@@ -144,7 +144,7 @@ def _close_logger(logger: logging.LoggerAdapter):
 
 _INT_DTYPES = [int, np.int32, np.int64]
 _FLOAT_DTYPES = [float, np.float64]
-_STR_DTYPES = [str, np.string_]
+_STR_DTYPES = [str, np.bytes_]
 
 # -- Dataset creators  ---------------------------------------