diff --git a/contracts/NonfungiblePositionManagerV4.sol b/contracts/NonfungiblePositionManagerV4.sol
index c23464bf..29c0153c 100644
--- a/contracts/NonfungiblePositionManagerV4.sol
+++ b/contracts/NonfungiblePositionManagerV4.sol
@@ -10,6 +10,7 @@ import {Currency, CurrencyLibrary} from "@uniswap/v4-core/contracts/types/Curren
 import {BalanceDelta} from "@uniswap/v4-core/contracts/types/BalanceDelta.sol";
 import {TickMath} from "@uniswap/v4-core/contracts/libraries/TickMath.sol";
 import {PoolId, PoolIdLibrary} from "@uniswap/v4-core/contracts/types/PoolId.sol";
+import {Position} from "@uniswap/v4-core/contracts/libraries/Position.sol";
 
 import {INonfungiblePositionManagerV4} from "./interfaces/INonfungiblePositionManagerV4.sol";
 import {PeripheryValidation} from "./base/PeripheryValidation.sol";
@@ -35,6 +36,7 @@ contract NonfungiblePositionManagerV4 is
     error NotApproved();
     error NotCleared();
     error NonexistentToken();
+    error Slippage(); // TODO: rename this to be more descriptive?
 
     // details about the Uniswap position
     struct TokenPosition {
@@ -151,6 +153,9 @@ contract NonfungiblePositionManagerV4 is
             settleDeltas(data.sender, params.poolKey, delta);
             return abi.encode(tokenId, liquidity, delta.amount0(), delta.amount1());
         }
+
+        // TODO: implement add liquidity
+        return abi.encode(0);
     }
 
     /// @inheritdoc INonfungiblePositionManagerV4
@@ -169,11 +174,13 @@ contract NonfungiblePositionManagerV4 is
         checkDeadline(params.deadline)
         returns (uint256 tokenId, uint128 liquidity, uint256 amount0, uint256 amount1)
     {
-        (tokenId, liquidity, amount0, amount1) =
-            poolManager.lock(abi.encode(CallbackData(CallbackAction.Mint, msg.sender, abi.encode(params))));
+        (tokenId, liquidity, amount0, amount1) = abi.decode(
+            poolManager.lock(abi.encode(CallbackData(CallbackAction.Mint, msg.sender, abi.encode(params)))),
+            (uint256, uint128, uint256, uint256)
+        );
     }
 
-    function mintCallback(MintParams calldata params)
+    function mintCallback(MintParams memory params)
         internal
         returns (uint256 tokenId, uint128 liquidity, BalanceDelta delta)
     {
@@ -186,12 +193,28 @@ contract NonfungiblePositionManagerV4 is
                 amount0Desired: params.amount0Desired,
                 amount1Desired: params.amount1Desired,
                 amount0Min: params.amount0Min,
-                amount1Min: params.amount1Min
+                amount1Min: params.amount1Min,
+                hookData: params.hookData
             })
         );
 
         tokenId = _nextId++;
-        _mint(tokenId);
+        _mint(params.recipient, tokenId);
+
+        Position.Info memory positionInfo =
+            poolManager.getPosition(poolId, address(this), params.tickLower, params.tickUpper);
+        _positions[tokenId] = TokenPosition({
+            nonce: 0,
+            operator: address(0),
+            poolId: poolId,
+            tickLower: params.tickLower,
+            tickUpper: params.tickUpper,
+            liquidity: liquidity,
+            feeGrowthInside0LastX128: positionInfo.feeGrowthInside0LastX128,
+            feeGrowthInside1LastX128: positionInfo.feeGrowthInside1LastX128,
+            tokensOwed0: 0,
+            tokensOwed1: 0
+        });
     }
 
     modifier isAuthorizedForToken(uint256 tokenId) {
@@ -294,10 +317,8 @@ contract NonfungiblePositionManagerV4 is
             IPoolManager.ModifyPositionParams(params.tickLower, params.tickUpper, int256(int128(liquidity))),
             params.hookData
         );
-        require(
-            uint256(int256(delta.amount0())) >= params.amount0Min
-                && uint256(int256(delta.amount1())) >= params.amount1Min,
-            "Price slippage check"
-        );
+        if (
+            uint256(int256(delta.amount0())) < params.amount0Min || uint256(int256(delta.amount1())) < params.amount1Min
+        ) revert Slippage();
     }
 }