diff --git a/ellipticcurve/utils/compatibility.py b/ellipticcurve/utils/compatibility.py
index 3b22dd3..06815b2 100644
--- a/ellipticcurve/utils/compatibility.py
+++ b/ellipticcurve/utils/compatibility.py
@@ -9,9 +9,13 @@
     intTypes = (int, float)
 
     def toString(string, encoding="utf-8"):
+        if isinstance(string,str):
+            return string
         return string.decode(encoding)
 
     def toBytes(string, encoding="utf-8"):
+        if isinstance(string,bytes):
+            return string
         return string.encode(encoding)
 
     def safeBinaryFromHex(hexadecimal):