diff --git a/contracts/Errors/OracleAggregatorErrors.sol b/contracts/Errors/OracleAggregatorErrors.sol
index 1902ae8..9c321fa 100644
--- a/contracts/Errors/OracleAggregatorErrors.sol
+++ b/contracts/Errors/OracleAggregatorErrors.sol
@@ -6,4 +6,6 @@ contract OracleAggregatorErrors {
     string constant internal ERROR_ORACLE_AGGREGATOR_QUERY_WAS_ALREADY_MADE = "ORACLE_AGGREGATOR:QUERY_WAS_ALREADY_MADE";
 
     string constant internal ERROR_ORACLE_AGGREGATOR_DATA_DOESNT_EXIST = "ORACLE_AGGREGATOR:DATA_DOESNT_EXIST";
+
+    string constant internal ERROR_ORACLE_AGGREGATOR_DATA_ALREADY_EXIST = "ORACLE_AGGREGATOR:DATA_ALREADY_EXIST";
 }
diff --git a/contracts/OracleAggregator.sol b/contracts/OracleAggregator.sol
index b64547c..059bf0d 100644
--- a/contracts/OracleAggregator.sol
+++ b/contracts/OracleAggregator.sol
@@ -69,6 +69,9 @@ contract OracleAggregator is OracleAggregatorErrors, ReentrancyGuard {
     /// @param timestamp uint256 Timestamp of data
     /// @param data uint256 Data itself
     function __callback(uint256 timestamp, uint256 data) public {
+        // Don't allow to push data twice
+        require(!dataExist[msg.sender][timestamp], ERROR_ORACLE_AGGREGATOR_DATA_ALREADY_EXIST);
+
         // Saving data
         dataCache[msg.sender][timestamp] = data;
 
diff --git a/test/OracleAggregator.js b/test/OracleAggregator.js
index d7db59c..46a8e97 100644
--- a/test/OracleAggregator.js
+++ b/test/OracleAggregator.js
@@ -53,6 +53,15 @@ contract('OracleAggregator', accounts => {
         assert.equal(result, data, 'Oracle didn\'t provided correct information')
     })
 
+    it('should reject attempt to push data twice', async () => {
+        try {
+            await oracleAggregator.__callback(timestamp, data, { from: oracle })
+            throw null
+        } catch (e) {
+            assert.ok(e.message.match(/ORACLE_AGGREGATOR:DATA_ALREADY_EXIST/), 'ORACLE_AGGREGATOR:DATA_ALREADY_EXIST')
+        }
+    })
+
     it('should correctly return fetchPrice from oracle', async () => {
         const result = await oracleAggregator.calculateFetchPrice.call(oracleIdMock.address)
         assert.equal(result, fetchPrice, 'Fetch price is not correct')