diff --git a/contracts/WakuRln.sol b/contracts/WakuRln.sol
index 765e408..21d5291 100644
--- a/contracts/WakuRln.sol
+++ b/contracts/WakuRln.sol
@@ -2,7 +2,7 @@
 pragma solidity 0.8.15;
 
 import {IPoseidonHasher} from "rln-contract/PoseidonHasher.sol";
-import {RlnBase, DuplicateIdCommitment} from "rln-contract/RlnBase.sol";
+import {RlnBase, DuplicateIdCommitment, FullTree} from "rln-contract/RlnBase.sol";
 import {Ownable} from "openzeppelin-contracts/contracts/access/Ownable.sol";
 
 error NotImplemented();
@@ -25,7 +25,7 @@ contract WakuRln is Ownable, RlnBase {
         idCommitmentIndex += 1;
     }
 
-    function register(uint256[] memory idCommitments) external onlyOwner {
+    function register(uint256[] calldata idCommitments) external onlyOwner {
         uint256 len = idCommitments.length;
         for (uint256 i = 0; i < len;) {
             _register(idCommitments[i]);
@@ -45,6 +45,7 @@ contract WakuRln is Ownable, RlnBase {
 
     function _validateRegistration(uint256 idCommitment) internal view override {
         if (members[idCommitment] != 0) revert DuplicateIdCommitment();
+        if (idCommitmentIndex >= SET_SIZE) revert FullTree();
     }
 
     function _validateSlash(uint256 idCommitment, address payable receiver, uint256[8] calldata proof)
diff --git a/contracts/WakuRlnRegistry.sol b/contracts/WakuRlnRegistry.sol
index a4f1094..ae48ec2 100644
--- a/contracts/WakuRlnRegistry.sol
+++ b/contracts/WakuRlnRegistry.sol
@@ -4,7 +4,6 @@ pragma solidity 0.8.15;
 import {WakuRln} from "./WakuRln.sol";
 import {IPoseidonHasher} from "rln-contract/PoseidonHasher.sol";
 import {Ownable} from "openzeppelin-contracts/contracts/access/Ownable.sol";
-import "forge-std/console.sol";
 
 error StorageAlreadyExists(address storageAddress);
 error NoStorageContractAvailable();
@@ -56,12 +55,28 @@ contract WakuRlnRegistry is Ownable {
                     assembly {
                         revert(add(32, err), mload(err))
                     }
+                    // when there are no further storage contracts available, revert
+                } else if (usingStorageIndex + 1 >= nextStorageIndex) {
+                    revert NoStorageContractAvailable();
                 }
                 usingStorageIndex += 1;
             }
         }
     }
 
+    function register(uint16 storageIndex, uint256[] calldata commitments) external payable {
+        if (storageIndex >= nextStorageIndex) revert NoStorageContractAvailable();
+        WakuRln(storages[storageIndex]).register(commitments);
+    }
+
+    function register(uint16 storageIndex, uint256 commitment) external payable {
+        if (storageIndex >= nextStorageIndex) revert NoStorageContractAvailable();
+        // optimize the gas used below
+        uint256[] memory commitments = new uint256[](1);
+        commitments[0] = commitment;
+        WakuRln(storages[storageIndex]).register(commitments);
+    }
+
     function forceProgress() external onlyOwner {
         if (usingStorageIndex >= nextStorageIndex) revert NoStorageContractAvailable();
         usingStorageIndex += 1;
diff --git a/docs/index.md b/docs/index.md
index 0b17306..c934859 100644
--- a/docs/index.md
+++ b/docs/index.md
@@ -178,6 +178,18 @@ function newStorage() external
 function register(uint256[] commitments) external payable
 ```
 
+### register
+
+```solidity
+function register(uint16 storageIndex, uint256[] commitments) external payable
+```
+
+### register
+
+```solidity
+function register(uint16 storageIndex, uint256 commitment) external payable
+```
+
 ### forceProgress
 
 ```solidity
diff --git a/foundry.toml b/foundry.toml
index b58d672..7d129c5 100644
--- a/foundry.toml
+++ b/foundry.toml
@@ -7,4 +7,6 @@ cache_path  = 'cache_forge'
 
 # 5667: Unused function parameter. Remove or comment out the variable name to silence this warning.
 # 5740: Unreachable code.
-ignored_error_codes = [5667, 5740]
\ No newline at end of file
+ignored_error_codes = [5667, 5740]
+# setting this to allow expensive larger inserts during tests
+memory_limit = 100_000_000
diff --git a/test/WakuRlnRegistry.t.sol b/test/WakuRlnRegistry.t.sol
index e83fd16..e49d536 100644
--- a/test/WakuRlnRegistry.t.sol
+++ b/test/WakuRlnRegistry.t.sol
@@ -3,12 +3,14 @@ pragma solidity ^0.8.15;
 
 import "../contracts/WakuRlnRegistry.sol";
 import {PoseidonHasher} from "rln-contract/PoseidonHasher.sol";
-import {DuplicateIdCommitment} from "rln-contract/RlnBase.sol";
+import {DuplicateIdCommitment, FullTree} from "rln-contract/RlnBase.sol";
 import {noDuplicate} from "./utils.sol";
 import "forge-std/Test.sol";
 import "forge-std/StdCheats.sol";
 
 contract WakuRlnRegistryTest is Test {
+    using stdStorage for StdStorage;
+
     WakuRlnRegistry public wakuRlnRegistry;
     PoseidonHasher public poseidonHasher;
 
@@ -40,7 +42,7 @@ contract WakuRlnRegistryTest is Test {
         wakuRlnRegistry.register(commitments);
     }
 
-    function test__BadRegister(uint256[] calldata commitments) public {
+    function test__InvalidRegistration_Duplicate(uint256[] calldata commitments) public {
         vm.assume(!noDuplicate(commitments));
         wakuRlnRegistry.newStorage();
         vm.expectRevert(DuplicateIdCommitment.selector);
@@ -52,4 +54,50 @@ contract WakuRlnRegistryTest is Test {
         wakuRlnRegistry.forceProgress();
         require(wakuRlnRegistry.usingStorageIndex() == 1);
     }
+
+    function test__SingleRegistration(uint256 commitment) public {
+        wakuRlnRegistry.newStorage();
+        wakuRlnRegistry.register(0, commitment);
+    }
+
+    function test__InvalidSingleRegistration__NoStorageContract(uint256 commitment) public {
+        wakuRlnRegistry.newStorage();
+        vm.expectRevert(NoStorageContractAvailable.selector);
+        wakuRlnRegistry.register(1, commitment);
+    }
+
+    function test__InvalidSingleRegistration__Duplicate(uint256 commitment) public {
+        wakuRlnRegistry.newStorage();
+        wakuRlnRegistry.register(0, commitment);
+        vm.expectRevert(DuplicateIdCommitment.selector);
+        wakuRlnRegistry.register(0, commitment);
+    }
+
+    function test__InvalidSingleRegistration__FullTree() public {
+        vm.pauseGasMetering();
+        wakuRlnRegistry.newStorage();
+        WakuRln wakuRln = WakuRln(wakuRlnRegistry.storages(0));
+        uint256 setSize = wakuRln.SET_SIZE();
+        // setSize - 1 because RlnBase uses 1-indexing
+        for (uint256 i = 0; i < setSize - 1; i++) {
+            wakuRlnRegistry.register(0, i);
+        }
+        vm.resumeGasMetering();
+        vm.expectRevert(FullTree.selector);
+        wakuRlnRegistry.register(0, setSize);
+    }
+
+    function test__InvalidRegistration__NoStorageContract() public {
+        vm.pauseGasMetering();
+        wakuRlnRegistry.newStorage();
+        address storageContract = wakuRlnRegistry.storages(0);
+        uint256 setSize = WakuRln(storageContract).SET_SIZE();
+
+        uint256[] memory commitments = new uint256[](setSize);
+        for (uint256 i = 1; i < setSize; i++) {
+            commitments[i] = i;
+        }
+        vm.expectRevert(NoStorageContractAvailable.selector);
+        wakuRlnRegistry.register(commitments);
+    }
 }