diff --git a/contracts/MerkleTreeWithHistory.sol b/contracts/MerkleTreeWithHistory.sol
index 23412a2..68cea8a 100644
--- a/contracts/MerkleTreeWithHistory.sol
+++ b/contracts/MerkleTreeWithHistory.sol
@@ -58,7 +58,7 @@ contract MerkleTreeWithHistory {
 
   function _insert(uint256 leaf) internal {
     uint32 current_index = next_index;
-    require(current_index != 2**(levels - 1), "Merkle tree is full");
+    require(current_index != 2**(levels - 1), "Merkle tree is full. No more leafs can be added");
     next_index += 1;
     uint256 current_level_hash = leaf;
     uint256 left;
diff --git a/test/MerkleTreeWithHistory.test.js b/test/MerkleTreeWithHistory.test.js
index 742c00c..82d8481 100644
--- a/test/MerkleTreeWithHistory.test.js
+++ b/test/MerkleTreeWithHistory.test.js
@@ -185,10 +185,10 @@ contract('MerkleTreeWithHistory', accounts => {
       }
 
       let error = await merkleTreeWithHistory.insert(1337).should.be.rejected
-      error.reason.should.be.equal('Merkle tree is full')
+      error.reason.should.be.equal('Merkle tree is full. No more leafs can be added')
 
       error = await merkleTreeWithHistory.insert(1).should.be.rejected
-      error.reason.should.be.equal('Merkle tree is full')
+      error.reason.should.be.equal('Merkle tree is full. No more leafs can be added')
     })
 
     it.skip('mimc gas', async () => {