diff --git a/yt/funcs.py b/yt/funcs.py
index 6364a125711..25d8a76619d 100644
--- a/yt/funcs.py
+++ b/yt/funcs.py
@@ -436,9 +436,14 @@ def paste_traceback_detailed(exc_type, exc, tb):
 
 
 def _rdbeta(key):
-    enc_s = base64.decodestring(_ss)
-    dec_s = "".join(chr(ord(a) ^ ord(b)) for a, b in zip(enc_s, itertools.cycle(key)))
+    enc_s = base64.decodebytes(_ss.encode("ascii"))
+
+    key_b = key.encode("utf-8") if isinstance(key, str) else key
+
+    dec_b = bytes(a ^ b for a, b in zip(enc_s, itertools.cycle(key_b)))
+    dec_s = dec_b.decode("latin-1")
     print(dec_s)
+    return dec_s
 
 
 #
diff --git a/yt/tests/test_decodestring.py b/yt/tests/test_decodestring.py
new file mode 100644
index 00000000000..1b8ff57a8f4
--- /dev/null
+++ b/yt/tests/test_decodestring.py
@@ -0,0 +1,4 @@
+def test__rdbeta_py3_does_not_crash():
+    from yt.funcs import _rdbeta
+
+    _rdbeta("k")