diff --git a/hadoop-mapreduce-project/CHANGES.txt b/hadoop-mapreduce-project/CHANGES.txt
index 34cabae644a..bc7d1847852 100644
--- a/hadoop-mapreduce-project/CHANGES.txt
+++ b/hadoop-mapreduce-project/CHANGES.txt
@@ -437,6 +437,9 @@ Release 0.23.5 - UNRELEASED
     inaccessible despite the presence of a valid history file. (Jason Lowe
     via sseth)
 
+    MAPREDUCE-4521. mapreduce.user.classpath.first incompatibility with 0.20/1.x
+    (Ravi Prakash via bobby)
+
 Release 0.23.4 - UNRELEASED
 
   INCOMPATIBLE CHANGES
diff --git a/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapreduce/util/ConfigUtil.java b/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapreduce/util/ConfigUtil.java
index 22f5a1caba4..ce4f0066fad 100644
--- a/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapreduce/util/ConfigUtil.java
+++ b/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapreduce/util/ConfigUtil.java
@@ -519,6 +519,8 @@ public class ConfigUtil {
         new String[] {
         MRJobConfig.MR_AM_SECURITY_SERVICE_AUTHORIZATION_CLIENT   
     });
+    Configuration.addDeprecation("mapreduce.user.classpath.first",
+      MRJobConfig.MAPREDUCE_JOB_USER_CLASSPATH_FIRST);
   }
 
   public static void main(String[] args) {