diff --git a/hadoop-mapreduce-project/CHANGES.txt b/hadoop-mapreduce-project/CHANGES.txt
index 3ffaad3e08e..93b23b832b3 100644
--- a/hadoop-mapreduce-project/CHANGES.txt
+++ b/hadoop-mapreduce-project/CHANGES.txt
@@ -290,6 +290,9 @@ Release 2.0.0 - UNRELEASED
     MAPREDUCE-4148. MapReduce should not have a compile-time dependency on
     HDFS. (tomwhite)
 
+    MAPREDUCE-4250. hadoop-config.sh missing variable exports, causes Yarn 
+    jobs to fail with ClassNotFoundException MRAppMaster. (phunt via tucu)
+
 Release 0.23.3 - UNRELEASED
 
   INCOMPATIBLE CHANGES
diff --git a/hadoop-mapreduce-project/hadoop-yarn/bin/yarn-config.sh b/hadoop-mapreduce-project/hadoop-yarn/bin/yarn-config.sh
index 934a461b645..275869f7365 100644
--- a/hadoop-mapreduce-project/hadoop-yarn/bin/yarn-config.sh
+++ b/hadoop-mapreduce-project/hadoop-yarn/bin/yarn-config.sh
@@ -49,7 +49,7 @@ then
 fi
  
 # Allow alternate conf dir location.
-YARN_CONF_DIR="${HADOOP_CONF_DIR:-$YARN_HOME/conf}"
+export YARN_CONF_DIR="${HADOOP_CONF_DIR:-$YARN_HOME/conf}"
 
 #check to see it is specified whether to use the slaves or the
 # masters file