diff --git a/CHANGES.txt b/CHANGES.txt
index 5e9edfdbec..48cd54a60d 100644
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -55,6 +55,7 @@
  * Fix repair -snapshot not working (CASSANDRA-5512)
  * Set isRunning flag later in binary protocol server (CASSANDRA-5467)
  * Fix use of CQL3 functions with descencind clustering order (CASSANDRA-5472)
+ * Prevent repair when protocol version does not match (CASSANDRA-5523)
 Merged from 1.1
  * Add retry mechanism to OTC for non-droppable_verbs (CASSANDRA-5393)
  * Use allocator information to improve memtable memory usage estimate
diff --git a/src/java/org/apache/cassandra/service/ActiveRepairService.java b/src/java/org/apache/cassandra/service/ActiveRepairService.java
index b692ab0c77..1752911e7e 100644
--- a/src/java/org/apache/cassandra/service/ActiveRepairService.java
+++ b/src/java/org/apache/cassandra/service/ActiveRepairService.java
@@ -658,6 +658,15 @@ public class ActiveRepairService
                     logger.error(String.format("[repair #%s] ", getName()) + message);
                     throw new IOException(message);
                 }
+
+                // All endpoints should be on the same protocol version
+                if (!MessagingService.instance().knowsVersion(endpoint) || MessagingService.instance().getVersion(endpoint) != MessagingService.current_version)
+                {
+                    String message = "Cannot repair among different protocol versions";
+                    differencingDone.signalAll();
+                    logger.error(String.format("[repair #%s] ", getName()) + message);
+                    throw new IOException(message);
+                }
             }
 
             ActiveRepairService.instance.sessions.put(getName(), this);