diff --git a/oak-core/src/main/java/org/apache/jackrabbit/oak/plugins/memory/AbstractBlob.java b/oak-core/src/main/java/org/apache/jackrabbit/oak/plugins/memory/AbstractBlob.java
index bac22b0..b8643e3 100644
--- a/oak-core/src/main/java/org/apache/jackrabbit/oak/plugins/memory/AbstractBlob.java
+++ b/oak-core/src/main/java/org/apache/jackrabbit/oak/plugins/memory/AbstractBlob.java
@@ -57,10 +57,15 @@ public abstract class AbstractBlob implements Blob {
         String ai = a.getContentIdentity();
         String bi = b.getContentIdentity();
 
-        //Check for identity first. If they are same then its
-        //definitely same blob. If not we need to check further.
-        if (ai != null && bi != null && ai.equals(bi)){
-            return true;
+        //Check for identity first.  If both identities exist,
+        //the blobs are equal if the identities are equal, and
+        //the blobs are not equal if the identities are not
+        //equal.
+        //This is because the identities are currently a
+        //hash of the blob content.  If this were to ever change
+        //this would also need to revert to the old mechanism.
+        if (ai != null && bi != null) {
+            return ai.equals(bi);
         }
 
         try {
diff --git a/oak-core/src/test/java/org/apache/jackrabbit/oak/plugins/memory/AbstractBlobTest.java b/oak-core/src/test/java/org/apache/jackrabbit/oak/plugins/memory/AbstractBlobTest.java
index 6f0dbf8..3aea0ac 100644
--- a/oak-core/src/test/java/org/apache/jackrabbit/oak/plugins/memory/AbstractBlobTest.java
+++ b/oak-core/src/test/java/org/apache/jackrabbit/oak/plugins/memory/AbstractBlobTest.java
@@ -39,11 +39,20 @@ public class AbstractBlobTest {
         byte[] data = bytes(100);
         Blob a = new TestBlob(data, "id1", false);
         Blob b = new TestBlob(data, "id1", false);
+        // Blobs are considered equal if their identities are equal.
         assertTrue(AbstractBlob.equal(a, b));
 
-        Blob a2 = new TestBlob(data, "id1", true);
-        Blob b2 = new TestBlob(data, "id2", true);
-        assertTrue("Blobs with different id but same content should match", AbstractBlob.equal(a2, b2));
+        Blob a2 = new TestBlob(data, "id1", false);
+        Blob b2 = new TestBlob(data, "id2", false);
+        // Blobs are not considered equal if their identities are not equal.  (See OAK-5253)
+        assertFalse(AbstractBlob.equal(a2, b2));
+
+        Blob a3 = new TestBlob(data, "id1", true);
+        Blob b3 = new TestBlob(data, "id2", true);
+        // As of OAK-5253, Blobs are not considered equal if their identities are not equal,
+        // even if the content is equal.  This is an optimization based on the implementation
+        // where blob identities are a hash of the content.
+        assertFalse("Blobs with different id but same content should not match", AbstractBlob.equal(a3, b3));
     }
 
     @Test