diff --git a/src/main/java/net/onrc/onos/datastore/WrongVersionException.java b/src/main/java/net/onrc/onos/datastore/WrongVersionException.java
new file mode 100644
index 0000000..9b59ff1
--- /dev/null
+++ b/src/main/java/net/onrc/onos/datastore/WrongVersionException.java
@@ -0,0 +1,31 @@
+package net.onrc.onos.datastore;
+
+import net.onrc.onos.datastore.utils.ByteArrayUtil;
+
+/**
+ * Exception thrown when conditional operation failed due to version mismatch.
+ */
+public class WrongVersionException extends RejectRulesException {
+    private static final long serialVersionUID = -1644202495890190823L;
+
+    public WrongVersionException(final String message) {
+	super(message);
+    }
+
+    public WrongVersionException(final IKVTableID tableID, final byte[] key,
+	    final long expectedVersion, final Throwable cause) {
+	// It will be best if {@code cause} has actual version encountered, but
+	// doesn't currently.
+	super(ByteArrayUtil.toHexStringBuffer(key, ":") + " on table:"
+	        + tableID + " was expected to be version:" + expectedVersion,
+	        cause);
+    }
+
+    public WrongVersionException(final IKVTableID tableID, final byte[] key,
+	    final long expectedVersion, final long encounteredVersion) {
+	super(ByteArrayUtil.toHexStringBuffer(key, ":") + " on table:"
+	        + tableID + " was expected to be version:" + expectedVersion
+	        + " but found:" + encounteredVersion);
+    }
+
+}