diff --git a/py_order_utils/builders/order_builder.py b/py_order_utils/builders/order_builder.py
index 88dec6a..065e2b0 100644
--- a/py_order_utils/builders/order_builder.py
+++ b/py_order_utils/builders/order_builder.py
@@ -59,7 +59,10 @@ def build_order_signature(self, _order: Order) -> str:
         """
         Signs the order
         """
-        return "0x" + self.sign(self._create_struct_hash(_order))
+        sig = self.sign(self._create_struct_hash(_order))
+        if len(sig) > 2 and sig[:2] != "0x":
+            sig = f"0x{sig}"
+        return sig
 
     def build_signed_order(self, data: OrderData) -> SignedOrder:
         """