diff --git a/core/src/main/java/io/undertow/server/protocol/proxy/ProxyProtocolReadListener.java b/core/src/main/java/io/undertow/server/protocol/proxy/ProxyProtocolReadListener.java
index 4dd07dbaae..6315e55bc2 100644
--- a/core/src/main/java/io/undertow/server/protocol/proxy/ProxyProtocolReadListener.java
+++ b/core/src/main/java/io/undertow/server/protocol/proxy/ProxyProtocolReadListener.java
@@ -37,7 +37,7 @@ class ProxyProtocolReadListener implements ChannelListener<StreamSourceChannel>
 
     private static final byte[] NAME = "PROXY ".getBytes(StandardCharsets.US_ASCII);
     private static final String UNKNOWN = "UNKNOWN";
-    private static final String TCP = "TCP";
+    private static final String TCP4 = "TCP4";
     private static final String TCP_6 = "TCP6";
 
     private final StreamConnection streamConnection;
@@ -136,7 +136,7 @@ public void handleEvent(StreamSourceChannel streamSourceChannel) {
                                         stringBuilder.setLength(0);
                                         if (protocol.equals(UNKNOWN)) {
                                             parsingUnknown = true;
-                                        } else if (!protocol.equals(TCP) && !protocol.equals(TCP_6)) {
+                                        } else if (!protocol.equals(TCP4) && !protocol.equals(TCP_6)) {
                                             throw UndertowMessages.MESSAGES.invalidProxyHeader();
                                         }
                                     } else if (sourceAddress == null) {
@@ -234,7 +234,7 @@ private void callOpenListener(StreamConnection streamConnection, final PooledByt
     }
 
     static InetAddress parseAddress(String addressString, String protocol) throws IOException {
-        if (protocol.equals(TCP)) {
+        if (protocol.equals(TCP4)) {
             return NetworkUtils.parseIpv4Address(addressString);
         } else {
             return NetworkUtils.parseIpv6Address(addressString);
diff --git a/core/src/test/java/io/undertow/server/protocol/proxy/ProxyProtocolTestCase.java b/core/src/test/java/io/undertow/server/protocol/proxy/ProxyProtocolTestCase.java
index 45a6442af0..ad83733bc4 100644
--- a/core/src/test/java/io/undertow/server/protocol/proxy/ProxyProtocolTestCase.java
+++ b/core/src/test/java/io/undertow/server/protocol/proxy/ProxyProtocolTestCase.java
@@ -41,7 +41,7 @@ public void handleRequest(HttpServerExchange exchange) throws Exception {
             undertow.start();
             int port = ((InetSocketAddress) undertow.getListenerInfo().get(0).getAddress()).getPort();
             Socket s = new Socket(DefaultServer.getHostAddress(), port);
-            s.getOutputStream().write("PROXY TCP 1.2.3.4 5.6.7.8 444 555\r\nGET / HTTP/1.0\r\n\r\n".getBytes(StandardCharsets.US_ASCII));
+            s.getOutputStream().write("PROXY TCP4 1.2.3.4 5.6.7.8 444 555\r\nGET / HTTP/1.0\r\n\r\n".getBytes(StandardCharsets.US_ASCII));
             String result = FileUtils.readFile(s.getInputStream());
             Assert.assertTrue(result, result.contains("result: /1.2.3.4:444 /5.6.7.8:555"));
         } finally {
@@ -72,7 +72,7 @@ public void handleRequest(HttpServerExchange exchange) throws Exception {
             undertow.start();
             int port = ((InetSocketAddress) undertow.getListenerInfo().get(0).getAddress()).getPort();
             Socket s = new Socket(DefaultServer.getHostAddress(), port);
-            s.getOutputStream().write("PROXY TCP 1.2.3.4 5.6.7.8 444 555\r\n".getBytes(StandardCharsets.US_ASCII));
+            s.getOutputStream().write("PROXY TCP4 1.2.3.4 5.6.7.8 444 555\r\n".getBytes(StandardCharsets.US_ASCII));
             s = DefaultServer.getClientSSLContext().getSocketFactory().createSocket(s, DefaultServer.getHostAddress(), port, true);
             s.getOutputStream().write("GET / HTTP/1.0\r\n\r\n".getBytes(StandardCharsets.US_ASCII));
             String result = FileUtils.readFile(s.getInputStream());