diff --git a/contracts/FeralfileArtworkV4.sol b/contracts/FeralfileArtworkV4.sol
index ac2ca5e..1b02797 100644
--- a/contracts/FeralfileArtworkV4.sol
+++ b/contracts/FeralfileArtworkV4.sol
@@ -79,9 +79,9 @@ contract FeralfileExhibitionV4 is
     constructor(
         string memory name_,
         string memory symbol_,
-        address signer_,
         bool burnable_,
         bool bridgeable_,
+        address signer_,
         address vault_,
         address costReceiver_,
         string memory tokenBaseURI_,
@@ -195,7 +195,7 @@ contract FeralfileExhibitionV4 is
     }
 
     /// @notice Set vault contract
-    /// @dev don't allow to set signer as zero address
+    /// @dev don't allow to set vault as zero address
     function setVault(address vault_) external onlyOwner {
         require(
             vault_ != address(0),
@@ -217,13 +217,13 @@ contract FeralfileExhibitionV4 is
         );
     }
 
-    /// @notice Start token selling
+    /// @notice Start token sale
     function startSale() external onlyOwner {
         mintable = false;
         resumeSale();
     }
 
-    /// @notice Resume token selling
+    /// @notice Resume token sale
     function resumeSale() public onlyOwner {
         require(
             !mintable,
@@ -251,7 +251,7 @@ contract FeralfileExhibitionV4 is
         _selling = false;
     }
 
-    /// @notice Stop token selling and burn remaining tokens
+    /// @notice Stop token sale and burn remaining tokens
     function stopSaleAndBurn() external onlyOwner {
         pauseSale();
 
@@ -288,7 +288,7 @@ contract FeralfileExhibitionV4 is
             for (uint16 j = 0; j < seriesIds.length; j++) {
                 if (artwork.seriesId == seriesIds[j]) {
                     address to = recipientAddresses[j];
-                    _transfer(from, to, tokenId);
+                    _safeTransfer(from, to, tokenId, "");
                     break;
                 }
             }
@@ -373,12 +373,20 @@ contract FeralfileExhibitionV4 is
 
     /// @notice Update the base URI for all tokens
     function setTokenBaseURI(string memory baseURI_) external onlyOwner {
+        require(
+            bytes(tokenBaseURI).length > 0,
+            "ERC721Metadata: baseURI_ is empty"
+        );
         tokenBaseURI = baseURI_;
     }
 
     /// @notice the cost receiver address
     /// @param costReceiver_ - the address of cost receiver
     function setCostReceiver(address costReceiver_) external onlyOwner {
+        require(
+            costReceiver_ != address(0),
+            "FeralfileExhibitionV4: costReceiver_ is zero address"
+        );
         costReceiver = costReceiver_;
     }
 
diff --git a/migrations/301_feralfile_exhibition_v4_0.js b/migrations/301_feralfile_exhibition_v4_0.js
index d205395..160edac 100644
--- a/migrations/301_feralfile_exhibition_v4_0.js
+++ b/migrations/301_feralfile_exhibition_v4_0.js
@@ -1,21 +1,19 @@
-var FeralfileExhibitionV4 = artifacts.require('FeralfileExhibitionV4');
+var FeralfileExhibitionV4 = artifacts.require("FeralfileExhibitionV4");
 
-const argv = require('minimist')(process.argv.slice(2), {
-    string: ['exhibition_curator'],
+const argv = require("minimist")(process.argv.slice(2), {
+    string: ["exhibition_curator"],
 });
 
 module.exports = function (deployer) {
-    let exhibition_name = argv.exhibition_name || 'FFV4 Test';
-    let exhibition_symbol = argv.exhibition_symbol || 'FeralfileExhibitionV4';
+    let exhibition_name = argv.exhibition_name || "FFV4 Test";
+    let exhibition_symbol = argv.exhibition_symbol || "FeralfileExhibitionV4";
     let exhibition_signer =
-        argv.exhibition_signer ||
-        '0x6732389c6d47d01487dcDc96e2Cc6BAf108452f2';
+        argv.exhibition_signer || "0x6732389c6d47d01487dcDc96e2Cc6BAf108452f2";
     let exhibition_vault =
-        argv.exhibition_vault ||
-        '0x0c51e8becb17ba3203cd04d3fc31fcb90de412a1';
+        argv.exhibition_vault || "0x0c51e8becb17ba3203cd04d3fc31fcb90de412a1";
     let exhibition_cost_receiver =
         argv.exhibition_cost_receiver ||
-        '0x6732389c6d47d01487dcDc96e2Cc6BAf108452f2';
+        "0x6732389c6d47d01487dcDc96e2Cc6BAf108452f2";
     let burnable = argv.burnable || true;
     let bridgeable = argv.bridgeable || true;
 
@@ -23,14 +21,14 @@ module.exports = function (deployer) {
         FeralfileExhibitionV4,
         exhibition_name,
         exhibition_symbol,
-        exhibition_signer,
         burnable,
         bridgeable,
+        exhibition_signer,
         exhibition_vault,
         exhibition_cost_receiver,
-        'https://ipfs.bitmark.com/ipfs/QmaQegRqExfFx8zuR6yscxzUwQJUc96LuNNQiAMK9BsUQe',
-        'https://ipfs.bitmark.com/ipfs/QmaQegRqExfFx8zuR6yscxzUwQJUc96LuNNQiAMK9BsUQe',
+        "https://ipfs.bitmark.com/ipfs/QmaQegRqExfFx8zuR6yscxzUwQJUc96LuNNQiAMK9BsUQe",
+        "https://ipfs.bitmark.com/ipfs/QmaQegRqExfFx8zuR6yscxzUwQJUc96LuNNQiAMK9BsUQe",
         [1, 2, 3, 4],
-        [1000, 1000, 1000, 1000],
+        [1000, 1000, 1000, 1000]
     );
 };
diff --git a/test/feralfile_exhibition_v4.js b/test/feralfile_exhibition_v4.js
index 54d54db..55e1523 100644
--- a/test/feralfile_exhibition_v4.js
+++ b/test/feralfile_exhibition_v4.js
@@ -20,9 +20,9 @@ contract("FeralfileExhibitionV4_0", async (accounts) => {
             let contract = await FeralfileExhibitionV4.new(
                 "Feral File V4 Test",
                 "FFv4",
-                this.signer,
                 true,
                 true,
+                this.signer,
                 this.vault.address,
                 COST_RECEIVER,
                 TOKEN_BASE_URI,