diff --git a/hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/DistributedFileSystem.java b/hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/DistributedFileSystem.java
index f4ca2657d4..57fac4076a 100644
--- a/hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/DistributedFileSystem.java
+++ b/hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/DistributedFileSystem.java
@@ -581,7 +581,7 @@ public void concat(Path trg, Path [] psrcs) throws IOException {
       for (int i=0; i<psrcs.length; i++) {
         srcsStr[i] = getPathName(srcs[i]);
       }
-      dfs.concat(getPathName(trg), srcsStr);
+      dfs.concat(getPathName(absF), srcsStr);
     } catch (UnresolvedLinkException e) {
       // Exception could be from trg or any src.
       // Fully resolve trg and srcs. Fail if any of them are a symlink.
diff --git a/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt b/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
index 8862c8a5a8..d857c58e79 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
+++ b/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
@@ -3456,6 +3456,9 @@ Release 2.6.3 - UNRELEASED
     HDFS-8615. Correct HTTP method in WebHDFS document.
     (Brahma Reddy Battula via aajisaka)
 
+    HDFS-9431. DistributedFileSystem#concat fails if the target path is
+    relative. (Kazuho Fujii via aajisaka)
+
 Release 2.6.2 - 2015-10-28
 
   INCOMPATIBLE CHANGES
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/TestHDFSConcat.java b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/TestHDFSConcat.java
index 4685eb907c..ded00317ae 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/TestHDFSConcat.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/TestHDFSConcat.java
@@ -490,4 +490,17 @@ public void testConcatWithQuotaIncrease() throws IOException {
     Assert.assertEquals(blockSize * repl * (srcNum + 1),
         summary.getSpaceConsumed());
   }
+
+  @Test
+  public void testConcatRelativeTargetPath() throws IOException {
+    Path dir = new Path("/dir");
+    Path trg = new Path("trg");
+    Path src = new Path(dir, "src");
+    dfs.setWorkingDirectory(dir);
+    DFSTestUtil.createFile(dfs, trg, blockSize, REPL_FACTOR, 1);
+    DFSTestUtil.createFile(dfs, src, blockSize, REPL_FACTOR, 1);
+    dfs.concat(trg, new Path[]{src});
+    assertEquals(blockSize * 2, dfs.getFileStatus(trg).getLen());
+    assertFalse(dfs.exists(src));
+  }
 }