diff --git a/rskj-core/src/main/java/org/ethereum/core/BlockHeader.java b/rskj-core/src/main/java/org/ethereum/core/BlockHeader.java
index 96342b05050..fd163495204 100644
--- a/rskj-core/src/main/java/org/ethereum/core/BlockHeader.java
+++ b/rskj-core/src/main/java/org/ethereum/core/BlockHeader.java
@@ -515,7 +515,7 @@ public byte[] getHashForMergedMining() {
     }
 
     private byte[] getHashRootForMergedMining(byte[] leftHash) {
-        if ((ummRoot.length != UMM_LEAVES_LENGTH) && (ummRoot.length != 0)){
+        if (ummRoot.length != UMM_LEAVES_LENGTH){
             throw new IllegalStateException(
                     String.format("UMM Root length must be either 0 or 20. Found: %d", ummRoot.length)
             );
diff --git a/rskj-core/src/test/java/co/rsk/core/BlockHeaderTest.java b/rskj-core/src/test/java/co/rsk/core/BlockHeaderTest.java
index 9e6fc5834e2..a704efe3592 100644
--- a/rskj-core/src/test/java/co/rsk/core/BlockHeaderTest.java
+++ b/rskj-core/src/test/java/co/rsk/core/BlockHeaderTest.java
@@ -217,6 +217,18 @@ public void getHashForMergedMiningWhenUmmRoot() {
         assertThat(header.getHashForMergedMining(), is(newHashForMergedMining));
     }
 
+    @Test
+    public void getHashForMergedMiningWhenEmptyUmmRoot() {
+        byte[] ummRoot = new byte[0];
+
+        BlockHeader header = createBlockHeaderWithUmmRoot(ummRoot);
+
+        byte[] encodedBlock = header.getEncoded(false, false);
+        byte[] hashForMergedMining = HashUtil.keccak256(encodedBlock);
+
+        assertThat(header.getHashForMergedMining(), is(hashForMergedMining));
+    }
+
     @Test(expected = IllegalStateException.class)
     public void getHashForMergedMiningWhenUmmRootWithLengthUnder20() {
         byte[] ummRoot = new byte[]{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18};