diff --git a/consensus/ibft/src/main/java/tech/pegasys/pantheon/consensus/ibft/statemachine/IbftBlockHeightManager.java b/consensus/ibft/src/main/java/tech/pegasys/pantheon/consensus/ibft/statemachine/IbftBlockHeightManager.java
index b98d464a46..733eb2419c 100644
--- a/consensus/ibft/src/main/java/tech/pegasys/pantheon/consensus/ibft/statemachine/IbftBlockHeightManager.java
+++ b/consensus/ibft/src/main/java/tech/pegasys/pantheon/consensus/ibft/statemachine/IbftBlockHeightManager.java
@@ -236,7 +236,7 @@ public class IbftBlockHeightManager {
       if (messageAge == FUTURE_ROUND) {
         startNewRound(payload.getRoundIdentifier().getRoundNumber());
       }
-      currentRound.handleProposalMessage(payload.getProposalPayload());
+      currentRound.handleProposalFromNewRound(signedPayload);
     }
   }
 
diff --git a/consensus/ibft/src/main/java/tech/pegasys/pantheon/consensus/ibft/statemachine/IbftRound.java b/consensus/ibft/src/main/java/tech/pegasys/pantheon/consensus/ibft/statemachine/IbftRound.java
index 96f5d81ca5..b9d7cc4d85 100644
--- a/consensus/ibft/src/main/java/tech/pegasys/pantheon/consensus/ibft/statemachine/IbftRound.java
+++ b/consensus/ibft/src/main/java/tech/pegasys/pantheon/consensus/ibft/statemachine/IbftRound.java
@@ -23,6 +23,7 @@ import tech.pegasys.pantheon.consensus.ibft.blockcreation.IbftBlockCreator;
 import tech.pegasys.pantheon.consensus.ibft.network.IbftMessageTransmitter;
 import tech.pegasys.pantheon.consensus.ibft.payload.CommitPayload;
 import tech.pegasys.pantheon.consensus.ibft.payload.MessageFactory;
+import tech.pegasys.pantheon.consensus.ibft.payload.NewRoundPayload;
 import tech.pegasys.pantheon.consensus.ibft.payload.PreparePayload;
 import tech.pegasys.pantheon.consensus.ibft.payload.PreparedCertificate;
 import tech.pegasys.pantheon.consensus.ibft.payload.ProposalPayload;
@@ -136,8 +137,26 @@ public class IbftRound {
 
   public void handleProposalMessage(final SignedData<ProposalPayload> msg) {
     LOG.info("Handling a Proposal message.");
+
+    if (getRoundIdentifier().getRoundNumber() != 0) {
+      LOG.info("Illegally received a Proposal message when not in Round 0.");
+      return;
+    }
+    actionReceivedProposal(msg);
+  }
+
+  public void handleProposalFromNewRound(final SignedData<NewRoundPayload> msg) {
+    LOG.info("Handling a New Round Proposal.");
+
+    if (getRoundIdentifier().getRoundNumber() == 0) {
+      LOG.info("Illegally received a NewRound message when in Round 0.");
+      return;
+    }
+    actionReceivedProposal(msg.getPayload().getProposalPayload());
+  }
+
+  private void actionReceivedProposal(final SignedData<ProposalPayload> msg) {
     final Block block = msg.getPayload().getBlock();
-    final boolean wasCommitted = roundState.isCommitted();
 
     if (updateStateWithProposedBlock(msg)) {
       LOG.info("Sending prepare message.");
@@ -147,10 +166,6 @@ public class IbftRound {
               roundState.getRoundIdentifier(), block.getHash());
       peerIsPrepared(localPrepareMessage);
     }
-
-    if (wasCommitted != roundState.isCommitted()) {
-      importBlockToChain();
-    }
   }
 
   public void handlePrepareMessage(final SignedData<PreparePayload> msg) {
@@ -169,6 +184,7 @@ public class IbftRound {
 
   private boolean updateStateWithProposedBlock(final SignedData<ProposalPayload> msg) {
     final boolean wasPrepared = roundState.isPrepared();
+    final boolean wasCommitted = roundState.isCommitted();
     final boolean blockAccepted = roundState.setProposedBlock(msg);
     if (blockAccepted) {
       // There are times handling a proposed block is enough to enter prepared.
@@ -177,6 +193,10 @@ public class IbftRound {
         final Block block = roundState.getProposedBlock().get();
         transmitter.multicastCommit(getRoundIdentifier(), block.getHash(), createCommitSeal(block));
       }
+      if (wasCommitted != roundState.isCommitted()) {
+        importBlockToChain();
+      }
+
       final SignedData<CommitPayload> localCommitMessage =
           messageFactory.createSignedCommitPayload(
               roundState.getRoundIdentifier(),
diff --git a/consensus/ibft/src/test/java/tech/pegasys/pantheon/consensus/ibft/statemachine/IbftRoundTest.java b/consensus/ibft/src/test/java/tech/pegasys/pantheon/consensus/ibft/statemachine/IbftRoundTest.java
index 1b21e5f4be..5b523674ec 100644
--- a/consensus/ibft/src/test/java/tech/pegasys/pantheon/consensus/ibft/statemachine/IbftRoundTest.java
+++ b/consensus/ibft/src/test/java/tech/pegasys/pantheon/consensus/ibft/statemachine/IbftRoundTest.java
@@ -67,7 +67,7 @@ import org.mockito.junit.MockitoJUnitRunner;
 public class IbftRoundTest {
 
   private final KeyPair localNodeKeys = KeyPair.generate();
-  private final ConsensusRoundIdentifier roundIdentifier = new ConsensusRoundIdentifier(1, 1);
+  private final ConsensusRoundIdentifier roundIdentifier = new ConsensusRoundIdentifier(1, 0);
   private final MessageFactory messageFactory = new MessageFactory(localNodeKeys);
   private final Subscribers<MinedBlockObserver> subscribers = new Subscribers<>();
   private ProtocolContext<IbftContext> protocolContext;
@@ -375,4 +375,55 @@ public class IbftRoundTest {
     round.createAndSendProposalMessage(15);
     verify(minedBlockObserver).blockMined(any());
   }
+
+  @Test
+  public void blockIsOnlyImportedOnceWhenCommitsAreReceivedBeforeProposal() {
+    final ConsensusRoundIdentifier roundIdentifier = new ConsensusRoundIdentifier(1, 0);
+    final int QUORUM_SIZE = 2;
+    final RoundState roundState = new RoundState(roundIdentifier, QUORUM_SIZE, messageValidator);
+    final IbftRound round =
+        new IbftRound(
+            roundState,
+            blockCreator,
+            protocolContext,
+            blockImporter,
+            subscribers,
+            localNodeKeys,
+            messageFactory,
+            transmitter);
+
+    round.handleCommitMessage(
+        messageFactory.createSignedCommitPayload(
+            roundIdentifier, proposedBlock.getHash(), remoteCommitSeal));
+
+    round.handleProposalMessage(
+        messageFactory.createSignedProposalPayload(roundIdentifier, proposedBlock));
+
+    verify(blockImporter, times(1)).importBlock(any(), any(), any());
+  }
+
+  @Test
+  public void blockIsImportedOnlyOnceIfQuorumCommitsAreReceivedPriorToProposal() {
+    final int QUORUM_SIZE = 1;
+    final RoundState roundState = new RoundState(roundIdentifier, QUORUM_SIZE, messageValidator);
+    final IbftRound round =
+        new IbftRound(
+            roundState,
+            blockCreator,
+            protocolContext,
+            blockImporter,
+            subscribers,
+            localNodeKeys,
+            messageFactory,
+            transmitter);
+
+    round.handleCommitMessage(
+        messageFactory.createSignedCommitPayload(
+            roundIdentifier, proposedBlock.getHash(), remoteCommitSeal));
+
+    round.handleProposalMessage(
+        messageFactory.createSignedProposalPayload(roundIdentifier, proposedBlock));
+
+    verify(blockImporter, times(1)).importBlock(any(), any(), any());
+  }
 }