diff --git a/contracts/JBToken.sol b/contracts/JBToken.sol
index 59320f933..0e44bcb12 100644
--- a/contracts/JBToken.sol
+++ b/contracts/JBToken.sol
@@ -82,7 +82,7 @@ contract JBToken is ERC20Votes, Ownable, IJBToken {
   /// @param _amount The amount of tokens to mint, as a fixed point number with 18 decimals.
   function mint(uint256 _projectId, address _account, uint256 _amount) external override onlyOwner {
     // Can't mint for a wrong project.
-    if (projectId != 0 && _projectId != projectId) revert BAD_PROJECT();
+    if (_projectId != projectId) revert BAD_PROJECT();
 
     return _mint(_account, _amount);
   }
@@ -94,7 +94,7 @@ contract JBToken is ERC20Votes, Ownable, IJBToken {
   /// @param _amount The amount of tokens to burn, as a fixed point number with 18 decimals.
   function burn(uint256 _projectId, address _account, uint256 _amount) external override onlyOwner {
     // Can't burn for a wrong project.
-    if (projectId != 0 && _projectId != projectId) revert BAD_PROJECT();
+    if (_projectId != projectId) revert BAD_PROJECT();
 
     return _burn(_account, _amount);
   }
@@ -105,7 +105,7 @@ contract JBToken is ERC20Votes, Ownable, IJBToken {
   /// @param _amount The amount the `_spender` is allowed to spend.
   function approve(uint256 _projectId, address _spender, uint256 _amount) external override {
     // Can't approve for a wrong project.
-    if (projectId != 0 && _projectId != projectId) revert BAD_PROJECT();
+    if (_projectId != projectId) revert BAD_PROJECT();
 
     approve(_spender, _amount);
   }
@@ -116,7 +116,7 @@ contract JBToken is ERC20Votes, Ownable, IJBToken {
   /// @param _amount The amount of the transfer, as a fixed point number with 18 decimals.
   function transfer(uint256 _projectId, address _to, uint256 _amount) external override {
     // Can't transfer for a wrong project.
-    if (projectId != 0 && _projectId != projectId) revert BAD_PROJECT();
+    if (_projectId != projectId) revert BAD_PROJECT();
 
     transfer(_to, _amount);
   }
@@ -133,7 +133,7 @@ contract JBToken is ERC20Votes, Ownable, IJBToken {
     uint256 _amount
   ) external override {
     // Can't transfer for a wrong project.
-    if (projectId != 0 && _projectId != projectId) revert BAD_PROJECT();
+    if (_projectId != projectId) revert BAD_PROJECT();
 
     transferFrom(_from, _to, _amount);
   }
diff --git a/contracts/JBTokenStore.sol b/contracts/JBTokenStore.sol
index 7b0f40d9f..a16e447dc 100644
--- a/contracts/JBTokenStore.sol
+++ b/contracts/JBTokenStore.sol
@@ -56,6 +56,10 @@ contract JBTokenStore is JBControllerUtility, JBOperatable, IJBTokenStore {
   /// @custom:param _projectId The ID of the project to which the token belongs.  
   mapping(uint256 => IJBToken) public override tokenOf;
 
+  /// @notice Each token's project.
+  /// @custom:param _token The address of the token to which the project belongs.
+  mapping(IJBToken => uint256) public override projectIdOf;
+
   /// @notice The total supply of unclaimed tokens for each project.
   /// @custom:param _projectId The ID of the project to which the token belongs.  
   mapping(uint256 => uint256) public override unclaimedTotalSupplyOf;
@@ -161,6 +165,9 @@ contract JBTokenStore is JBControllerUtility, JBOperatable, IJBTokenStore {
     // Store the token contract.
     tokenOf[_projectId] = token;
 
+    // Store the project for the token.
+    projectIdOf[token] = _projectId;
+
     emit Issue(_projectId, token, _name, _symbol, msg.sender);
   }
 
@@ -176,15 +183,21 @@ contract JBTokenStore is JBControllerUtility, JBOperatable, IJBTokenStore {
     // Can't set to the zero address.
     if (_token == IJBToken(address(0))) revert EMPTY_TOKEN();
 
-    // Can't set token if already set.
+    // Can't set token if the project is already associated with another token.
     if (tokenOf[_projectId] != IJBToken(address(0))) revert ALREADY_SET();
 
+    // Can't set token if its already associated with another project.
+    if (projectIdOf[_token] != 0) revert ALREADY_SET();
+
     // Can't change to a token that doesn't use 18 decimals.
     if (_token.decimals() != 18) revert TOKENS_MUST_HAVE_18_DECIMALS();
 
     // Store the new token.
     tokenOf[_projectId] = _token;
 
+    // Store the project for the token.
+    projectIdOf[_token] = _projectId;
+
     emit Set(_projectId, _token, msg.sender);
   }
 
diff --git a/contracts/interfaces/IJBTokenStore.sol b/contracts/interfaces/IJBTokenStore.sol
index 11ffbe247..7e4071ffb 100644
--- a/contracts/interfaces/IJBTokenStore.sol
+++ b/contracts/interfaces/IJBTokenStore.sol
@@ -54,6 +54,8 @@ interface IJBTokenStore {
 
   function tokenOf(uint256 projectId) external view returns (IJBToken);
 
+  function projectIdOf(IJBToken token) external view returns (uint256);
+
   function projects() external view returns (IJBProjects);
 
   function fundingCycleStore() external view returns (IJBFundingCycleStore);