diff --git a/java/google/registry/proxy/handler/ProxyProtocolHandler.java b/java/google/registry/proxy/handler/ProxyProtocolHandler.java
index f86760658..2612f14d3 100644
--- a/java/google/registry/proxy/handler/ProxyProtocolHandler.java
+++ b/java/google/registry/proxy/handler/ProxyProtocolHandler.java
@@ -81,6 +81,15 @@ public class ProxyProtocolHandler extends ByteToMessageDecoder {
           remoteIP = headerArray[2];
           logger.atFine().log(
               "Header parsed, using %s as remote IP for channel %s", remoteIP, ctx.channel());
+          // If the header is "PROXY UNKNOWN"
+          // (see https://www.haproxy.org/download/1.8/doc/proxy-protocol.txt), likely when the
+          // remote connection to the external load balancer is through special means, make it
+          // 0.0.0.0 so that it can be treated accordingly by the relevant quota configs.
+        } else if (headerArray.length == 2 && headerArray[1].equals("UNKNOWN")) {
+          logger.atFine().log(
+              "Header parsed, source IP unknown, using 0.0.0.0 as remote IP for channel %s",
+              ctx.channel());
+          remoteIP = "0.0.0.0";
         } else {
           logger.atFine().log(
               "Cannot parse the header, using source IP as remote IP for channel %s",
diff --git a/javatests/google/registry/proxy/handler/ProxyProtocolHandlerTest.java b/javatests/google/registry/proxy/handler/ProxyProtocolHandlerTest.java
index fa7b8f2bd..62c885d1b 100644
--- a/javatests/google/registry/proxy/handler/ProxyProtocolHandlerTest.java
+++ b/javatests/google/registry/proxy/handler/ProxyProtocolHandlerTest.java
@@ -57,7 +57,7 @@ public class ProxyProtocolHandlerTest {
     assertThat(channel.writeInbound(Unpooled.wrappedBuffer((header + message).getBytes(UTF_8))))
         .isTrue();
     assertThat(((ByteBuf) channel.readInbound()).toString(UTF_8)).isEqualTo(message);
-    assertThat(channel.attr(REMOTE_ADDRESS_KEY).get()).isNull();
+    assertThat(channel.attr(REMOTE_ADDRESS_KEY).get()).isEqualTo("0.0.0.0");
     assertThat(channel.pipeline().get(ProxyProtocolHandler.class)).isNull();
     assertThat(channel.isActive()).isTrue();
   }