diff --git a/src/protocol.h b/src/protocol.h
--- a/src/protocol.h
+++ b/src/protocol.h
@@ -339,7 +339,6 @@
 };
 
 /** getdata message type flags */
-const uint32_t MSG_EXT_FLAG = 1 << 29;
 const uint32_t MSG_TYPE_MASK = 0xffffffff >> 3;
 
 /** getdata / inv message types.
@@ -355,10 +354,6 @@
     MSG_FILTERED_BLOCK = 3,
     //!< Defined in BIP152
     MSG_CMPCT_BLOCK = 4,
-
-    //!< Extension block
-    MSG_EXT_TX = MSG_TX | MSG_EXT_FLAG,
-    MSG_EXT_BLOCK = MSG_BLOCK | MSG_EXT_FLAG,
 };
 
 /** inv message data */
diff --git a/src/protocol.cpp b/src/protocol.cpp
--- a/src/protocol.cpp
+++ b/src/protocol.cpp
@@ -207,7 +207,6 @@
 
 std::string CInv::GetCommand() const {
     std::string cmd;
-    if (type & MSG_EXT_FLAG) cmd.append("extblk-");
     switch (GetKind()) {
         case MSG_TX:
             return cmd.append(NetMsgType::TX);
diff --git a/src/test/inv_tests.cpp b/src/test/inv_tests.cpp
--- a/src/test/inv_tests.cpp
+++ b/src/test/inv_tests.cpp
@@ -24,8 +24,6 @@
               false, true);
     CheckType(GetDataMsg::MSG_CMPCT_BLOCK, GetDataMsg::MSG_CMPCT_BLOCK, false,
               true);
-    CheckType(GetDataMsg::MSG_EXT_TX, GetDataMsg::MSG_TX, true, false);
-    CheckType(GetDataMsg::MSG_EXT_BLOCK, GetDataMsg::MSG_BLOCK, false, true);
 }
 
 static void CheckCommand(int type, std::string expected) {
@@ -39,8 +37,6 @@
     CheckCommand(GetDataMsg::MSG_BLOCK, "block");
     CheckCommand(GetDataMsg::MSG_FILTERED_BLOCK, "merkleblock");
     CheckCommand(GetDataMsg::MSG_CMPCT_BLOCK, "cmpctblock");
-    CheckCommand(GetDataMsg::MSG_EXT_TX, "extblk-tx");
-    CheckCommand(GetDataMsg::MSG_EXT_BLOCK, "extblk-block");
 }
 
 BOOST_AUTO_TEST_SUITE_END()