diff --git a/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt b/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
index a8ae8ef082a..257a1445900 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
+++ b/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
@@ -1,7 +1,7 @@
 Hadoop HDFS Change Log
 
 Release 2.0.3-alpha - Unreleased
-  
+
   INCOMPATIBLE CHANGES
 
   NEW FEATURES
@@ -83,6 +83,9 @@ Release 2.0.3-alpha - Unreleased
     method for casting; avoiding creation of new empty lists; cleaning up 
     some code and rewriting some javadoc. (szetszwo)
 
+    HDFS-4121. Add namespace declarations in hdfs .proto files for languages 
+    other than java. (Binglin Chang via suresh)
+
   OPTIMIZATIONS
 
   BUG FIXES 
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/proto/ClientDatanodeProtocol.proto b/hadoop-hdfs-project/hadoop-hdfs/src/main/proto/ClientDatanodeProtocol.proto
index 99dcd146e5b..5392077b37a 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/proto/ClientDatanodeProtocol.proto
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/proto/ClientDatanodeProtocol.proto
@@ -23,6 +23,7 @@ option java_package = "org.apache.hadoop.hdfs.protocol.proto";
 option java_outer_classname = "ClientDatanodeProtocolProtos";
 option java_generic_services = true;
 option java_generate_equals_and_hash = true;
+package hadoop.hdfs;
 
 import "hdfs.proto";
 
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/proto/ClientNamenodeProtocol.proto b/hadoop-hdfs-project/hadoop-hdfs/src/main/proto/ClientNamenodeProtocol.proto
index 8a4fd96d461..3c97b0015ae 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/proto/ClientNamenodeProtocol.proto
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/proto/ClientNamenodeProtocol.proto
@@ -20,6 +20,7 @@ option java_package = "org.apache.hadoop.hdfs.protocol.proto";
 option java_outer_classname = "ClientNamenodeProtocolProtos";
 option java_generic_services = true;
 option java_generate_equals_and_hash = true;
+package hadoop.hdfs;
 
 import "hdfs.proto";
 
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/proto/DatanodeProtocol.proto b/hadoop-hdfs-project/hadoop-hdfs/src/main/proto/DatanodeProtocol.proto
index 65caa5beefb..a5695068bbf 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/proto/DatanodeProtocol.proto
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/proto/DatanodeProtocol.proto
@@ -23,6 +23,7 @@ option java_package = "org.apache.hadoop.hdfs.protocol.proto";
 option java_outer_classname = "DatanodeProtocolProtos";
 option java_generic_services = true;
 option java_generate_equals_and_hash = true;
+package hadoop.hdfs;
 
 import "hdfs.proto";
 
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/proto/GetUserMappingsProtocol.proto b/hadoop-hdfs-project/hadoop-hdfs/src/main/proto/GetUserMappingsProtocol.proto
index d3e2321f5a8..4ea1cec1b5a 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/proto/GetUserMappingsProtocol.proto
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/proto/GetUserMappingsProtocol.proto
@@ -20,6 +20,7 @@ option java_package = "org.apache.hadoop.hdfs.protocol.proto";
 option java_outer_classname = "GetUserMappingsProtocolProtos";
 option java_generic_services = true;
 option java_generate_equals_and_hash = true;
+package hadoop.hdfs;
 
 /**
  *  Get groups for user request.
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/proto/HAZKInfo.proto b/hadoop-hdfs-project/hadoop-hdfs/src/main/proto/HAZKInfo.proto
index 364c5bd2ef4..07bc9a93a82 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/proto/HAZKInfo.proto
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/proto/HAZKInfo.proto
@@ -17,6 +17,7 @@
  */
 option java_package = "org.apache.hadoop.hdfs.server.namenode.ha.proto";
 option java_outer_classname = "HAZKInfoProtos";
+package hadoop.hdfs;
 
 message ActiveNodeInfo {
   required string nameserviceId = 1;
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/proto/InterDatanodeProtocol.proto b/hadoop-hdfs-project/hadoop-hdfs/src/main/proto/InterDatanodeProtocol.proto
index 1e7c1e59b31..80419b96a60 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/proto/InterDatanodeProtocol.proto
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/proto/InterDatanodeProtocol.proto
@@ -23,6 +23,7 @@ option java_package = "org.apache.hadoop.hdfs.protocol.proto";
 option java_outer_classname = "InterDatanodeProtocolProtos";
 option java_generic_services = true;
 option java_generate_equals_and_hash = true;
+package hadoop.hdfs;
 
 import "hdfs.proto";
 
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/proto/JournalProtocol.proto b/hadoop-hdfs-project/hadoop-hdfs/src/main/proto/JournalProtocol.proto
index 1e720bab059..3db9460ea1f 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/proto/JournalProtocol.proto
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/proto/JournalProtocol.proto
@@ -23,6 +23,7 @@ option java_package = "org.apache.hadoop.hdfs.protocol.proto";
 option java_outer_classname = "JournalProtocolProtos";
 option java_generic_services = true;
 option java_generate_equals_and_hash = true;
+package hadoop.hdfs;
 
 import "hdfs.proto";
 
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/proto/NamenodeProtocol.proto b/hadoop-hdfs-project/hadoop-hdfs/src/main/proto/NamenodeProtocol.proto
index c54771bd9dd..62884c66815 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/proto/NamenodeProtocol.proto
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/proto/NamenodeProtocol.proto
@@ -23,6 +23,7 @@ option java_package = "org.apache.hadoop.hdfs.protocol.proto";
 option java_outer_classname = "NamenodeProtocolProtos";
 option java_generic_services = true;
 option java_generate_equals_and_hash = true;
+package hadoop.hdfs;
 
 import "hdfs.proto";
 
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/proto/RefreshAuthorizationPolicyProtocol.proto b/hadoop-hdfs-project/hadoop-hdfs/src/main/proto/RefreshAuthorizationPolicyProtocol.proto
index 45bfaf8576c..1e3fff8d5a2 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/proto/RefreshAuthorizationPolicyProtocol.proto
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/proto/RefreshAuthorizationPolicyProtocol.proto
@@ -20,6 +20,7 @@ option java_package = "org.apache.hadoop.hdfs.protocol.proto";
 option java_outer_classname = "RefreshAuthorizationPolicyProtocolProtos";
 option java_generic_services = true;
 option java_generate_equals_and_hash = true;
+package hadoop.hdfs;
 
 /**
  *  Refresh service acl request.
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/proto/RefreshUserMappingsProtocol.proto b/hadoop-hdfs-project/hadoop-hdfs/src/main/proto/RefreshUserMappingsProtocol.proto
index 4e45d523b52..70bf27e963c 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/proto/RefreshUserMappingsProtocol.proto
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/proto/RefreshUserMappingsProtocol.proto
@@ -20,6 +20,7 @@ option java_package = "org.apache.hadoop.hdfs.protocol.proto";
 option java_outer_classname = "RefreshUserMappingsProtocolProtos";
 option java_generic_services = true;
 option java_generate_equals_and_hash = true;
+package hadoop.hdfs;
 
 /**
  *  Refresh user to group mappings request.
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/proto/datatransfer.proto b/hadoop-hdfs-project/hadoop-hdfs/src/main/proto/datatransfer.proto
index 3ccad5efbe1..ae42c8358b3 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/proto/datatransfer.proto
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/proto/datatransfer.proto
@@ -22,6 +22,7 @@
 option java_package = "org.apache.hadoop.hdfs.protocol.proto";
 option java_outer_classname = "DataTransferProtos";
 option java_generate_equals_and_hash = true;
+package hadoop.hdfs;
 
 import "hdfs.proto";
 
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/proto/hdfs.proto b/hadoop-hdfs-project/hadoop-hdfs/src/main/proto/hdfs.proto
index 70a04752ffc..8e98f2c9aeb 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/proto/hdfs.proto
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/proto/hdfs.proto
@@ -22,6 +22,7 @@
 option java_package = "org.apache.hadoop.hdfs.protocol.proto";
 option java_outer_classname = "HdfsProtos";
 option java_generate_equals_and_hash = true;
+package hadoop.hdfs;
 
 /**
  * Extended block idenfies a block