diff --git a/hadoop-common-project/hadoop-common/CHANGES.txt b/hadoop-common-project/hadoop-common/CHANGES.txt
index 8e4d686717a..0d9dae14e58 100644
--- a/hadoop-common-project/hadoop-common/CHANGES.txt
+++ b/hadoop-common-project/hadoop-common/CHANGES.txt
@@ -110,6 +110,9 @@ Release 2.0.3-alpha - Unreleased
     HADOOP-8948. TestFileUtil.testGetDU fails on Windows due to incorrect
     assumption of line separator. (Chris Nauroth via suresh)
 
+    HADOOP-8951. RunJar to fail with user-comprehensible error 
+    message if jar missing. (stevel via suresh)
+
 Release 2.0.2-alpha - 2012-09-07 
 
   INCOMPATIBLE CHANGES
diff --git a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/util/RunJar.java b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/util/RunJar.java
index 7211b5bd706..ec1c6d84c0e 100644
--- a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/util/RunJar.java
+++ b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/util/RunJar.java
@@ -126,6 +126,10 @@ public class RunJar {
     int firstArg = 0;
     String fileName = args[firstArg++];
     File file = new File(fileName);
+    if (!file.exists() || !file.isFile()) {
+      System.err.println("Not a valid JAR: " + file.getCanonicalPath());
+      System.exit(-1);
+    }
     String mainClassName = null;
 
     JarFile jarFile;