diff --git a/contracts/MedianOracle.sol b/contracts/MedianOracle.sol
index 00ab8609..538a3cfc 100644
--- a/contracts/MedianOracle.sol
+++ b/contracts/MedianOracle.sol
@@ -108,13 +108,21 @@ contract MedianOracle is Ownable, IOracle {
         Report[2] storage reports = providerReports[providerAddress];
         uint256[2] memory timestamps = [reports[0].timestamp, reports[1].timestamp];
 
+        // Checks that this providerAddress is already whitelisted
         require(timestamps[0] > 0);
 
         uint8 index_recent = timestamps[0] >= timestamps[1] ? 0 : 1;
         uint8 index_past = 1 - index_recent;
 
+        uint256 minValidTimestamp = now.sub(reportExpirationTimeSec);
+        uint256 maxValidTimestamp = now.sub(reportDelaySec);
+
         // Check that the push is not too soon after the last one.
-        require(timestamps[index_recent].add(reportDelaySec) <= now);
+        // unless past one is already expired
+        require(
+            timestamps[index_past] < minValidTimestamp ||
+                timestamps[index_recent] <= maxValidTimestamp
+        );
 
         reports[index_past].timestamp = now;
         reports[index_past].payload = payload;
@@ -127,6 +135,7 @@ contract MedianOracle is Ownable, IOracle {
      */
     function purgeReports() external {
         address providerAddress = msg.sender;
+        // Check that this providerAddress is already whitelisted
         require(providerReports[providerAddress][0].timestamp > 0);
         providerReports[providerAddress][0].timestamp = 1;
         providerReports[providerAddress][1].timestamp = 1;
diff --git a/test/unit/MedianOracle.ts b/test/unit/MedianOracle.ts
index 19636f6b..d1f42e04 100644
--- a/test/unit/MedianOracle.ts
+++ b/test/unit/MedianOracle.ts
@@ -91,11 +91,55 @@ describe('MedianOracle:pushReport', async function () {
   it('should only push from authorized source', async function () {
     await expect(oracle.connect(A).pushReport(payload)).to.be.reverted
   })
-  it('should fail if reportDelaySec did not pass since the previous push', async function () {
+
+  it('should pass if reportDelaySec did not pass since the previous push, but previous report non-existent', async function () {
+    await oracle.addProvider(await A.getAddress())
+    await oracle.connect(A).pushReport(payload)
+    await oracle.connect(A).pushReport(payload)
+  })
+
+  it('should pass if reportDelaySec did pass since the previous push, and previous report non-existent', async function () {
     await oracle.addProvider(await A.getAddress())
     await oracle.connect(A).pushReport(payload)
+    await increaseTime(20)
+    await oracle.connect(A).pushReport(payload)
+  })
+
+  it('should pass if reportDelaySec did pass since the previous push, but previous report expired', async function () {
+    await oracle.addProvider(await A.getAddress())
+    await oracle.connect(A).pushReport(payload)
+    await increaseTime(70)
+    await oracle.connect(A).pushReport(payload)
+    await oracle.connect(A).pushReport(payload)
+  })
+
+  it('should pass if reportDelaySec did pass since the previous push, and previous report expired', async function () {
+    await oracle.addProvider(await A.getAddress())
+    await oracle.connect(A).pushReport(payload)
+    await increaseTime(70)
+    await oracle.connect(A).pushReport(payload)
+    await increaseTime(20)
+    await oracle.connect(A).pushReport(payload)
+  })
+
+  it('should fail if reportDelaySec did not pass since the previous push, and previous report not expired', async function () {
+    await oracle.addProvider(await A.getAddress())
+    await oracle.connect(A).pushReport(payload)
+    await increaseTime(20)
+    await oracle.connect(A).pushReport(payload)
+    await expect(oracle.connect(A).pushReport(payload)).to.be.reverted
+  })
+
+  it('should pass if reportDelaySec did pass since the previous push, and previous report not expired', async function () {
+    await oracle.addProvider(await A.getAddress())
+    await oracle.connect(A).pushReport(payload)
+    await increaseTime(20)
+    await oracle.connect(A).pushReport(payload)
+    await increaseTime(20)
+    await oracle.connect(A).pushReport(payload)
     await expect(oracle.connect(A).pushReport(payload)).to.be.reverted
   })
+
   it('should emit ProviderReportPushed message', async function () {
     oracle.addProvider(await A.getAddress())
     const tx = await oracle.connect(A).pushReport(payload)