diff --git a/contracts/exchange/contracts/src/MixinSignatureValidator.sol b/contracts/exchange/contracts/src/MixinSignatureValidator.sol
index 320c3cd05e..c0c45a332a 100644
--- a/contracts/exchange/contracts/src/MixinSignatureValidator.sol
+++ b/contracts/exchange/contracts/src/MixinSignatureValidator.sol
@@ -121,11 +121,11 @@ contract MixinSignatureValidator is
     /// @param signature Proof that the order has been signed by signer.
     /// @return True if the signature is valid for the given order and signer.
     function isValidOrderSignature(
-        Order calldata order,
+        Order memory order,
         address signerAddress,
-        bytes calldata signature
+        bytes memory signature
     )
-        external
+        public
         view
         returns (bool isValid)
     {
diff --git a/contracts/exchange/contracts/src/interfaces/ISignatureValidator.sol b/contracts/exchange/contracts/src/interfaces/ISignatureValidator.sol
index b9c6d5baf9..2685279338 100644
--- a/contracts/exchange/contracts/src/interfaces/ISignatureValidator.sol
+++ b/contracts/exchange/contracts/src/interfaces/ISignatureValidator.sol
@@ -64,11 +64,11 @@ contract ISignatureValidator {
     /// @param signature Proof of signing.
     /// @return Validity of order signature.
     function isValidOrderSignature(
-        LibOrder.Order calldata order,
+        LibOrder.Order memory order,
         address signerAddress,
-        bytes calldata signature
+        bytes memory signature
     )
-        external
+        public
         view
         returns (bool isValid);
 }