diff --git a/CHANGES b/CHANGES
index 17b379c..0ded833 100644
--- a/CHANGES
+++ b/CHANGES
@@ -1,6 +1,8 @@
   * New config param: relay.info.nips which allows you to override the NIPs
     that are claimed to be supported (requested by ismyhc)
   * New connectionTimeout parameter in router config (thanks Braydon Fuller!)
+  * Bugfix: IPv4-mapped IPv6 addresses in X-Real-IP headers were not parsed
+    correctly (reported by Petr Kracík)
 
 1.0.1
   * Prevent exporting a v2 DB using --fried. The packed representation will be
diff --git a/src/apps/relay/RelayWebsocket.cpp b/src/apps/relay/RelayWebsocket.cpp
index 6ba1503..b87de56 100644
--- a/src/apps/relay/RelayWebsocket.cpp
+++ b/src/apps/relay/RelayWebsocket.cpp
@@ -197,6 +197,11 @@ void RelayServer::runWebsocket(ThreadPool<MsgWebsocket>::Thread &thr) {
 
         if (cfg().relay__realIpHeader.size()) {
             auto header = req.getHeader(cfg().relay__realIpHeader.c_str()).toString(); // not string_view: parseIP needs trailing 0 byte
+
+            // HACK: uWebSockets strips leading : characters, which interferes with IPv6 parsing.
+            // This fixes it for the common ::1 and ::ffff:1.2.3.4 cases. FIXME: fix the underlying library.
+            if (header == "1" || header.starts_with("ffff:")) header = std::string("::") + header;
+
             c->ipAddr = parseIP(header);
             if (c->ipAddr.size() == 0) LW << "Couldn't parse IP from header " << cfg().relay__realIpHeader << ": " << header;
         }