diff --git a/README.html b/README.html
index d595faa..3f919e7 100644
--- a/README.html
+++ b/README.html
@@ -1261,9 +1261,13 @@ that your network <strong>does not have a running Bonjour/zeroconf
 DNS-SD server.</strong> Before v1.60, UxPlay used to stall silently if
 DNS-SD service registration failed, but now stops with an error message
 returned by the DNSServiceRegister function: kDNSServiceErr_Unknown if
-no DNS-SD server was found: other mDNS error codes are in the range FFFE
-FF00 (-65792) to FFFE FFFF (-65537), and are listed in the dnssd.h file.
-An older version of this (the one used by avahi) is found <a
+no DNS-SD server was found. (A NixOS user found that in NixOS, this
+error can also occur if avahi-daemon service IS running with publishing
+enabled, but reports “the error disappeared on NixOS by setting
+services.avahi.openFirewall to true”.) Other mDNS error codes are in the
+range FFFE FF00 (-65792) to FFFE FFFF (-65537), and are listed in the
+dnssd.h file. An older version of this (the one used by avahi) is found
+<a
 href="https://github.com/lathiat/avahi/blob/master/avahi-compat-libdns_sd/dns_sd.h">here</a>.
 A few additional error codes are defined in a later version from <a
 href="https://opensource.apple.com/source/mDNSResponder/mDNSResponder-544/mDNSShared/dns_sd.h.auto.html">Apple</a>.</p>
diff --git a/README.md b/README.md
index e00648d..0e03704 100644
--- a/README.md
+++ b/README.md
@@ -1002,8 +1002,10 @@ Some  systems  may instead use the mdnsd daemon as an alternative to provide DNS
 
 If UxPlay stops with the "No DNS-SD Server found" message, this  means that your network **does not have a running Bonjour/zeroconf DNS-SD server.**
 Before v1.60, UxPlay used to stall silently if DNS-SD service registration failed, but now stops with an error message returned by the
-DNSServiceRegister function: kDNSServiceErr_Unknown if no DNS-SD server was found:
-other mDNS error codes are in the range FFFE FF00 (-65792) to FFFE FFFF (-65537), and are listed in the
+DNSServiceRegister function: kDNSServiceErr_Unknown if no DNS-SD server was found.
+(A NixOS user found that in NixOS, this error can also occur if avahi-daemon service IS running with publishing enabled,
+but reports "the error disappeared on NixOS by setting services.avahi.openFirewall to true".)
+Other mDNS error codes are in the range FFFE FF00 (-65792) to FFFE FFFF (-65537), and are listed in the
 dnssd.h file.  An older version of this (the one used by avahi) is found [here](https://github.com/lathiat/avahi/blob/master/avahi-compat-libdns_sd/dns_sd.h).
 A few additional error codes are defined in a later version
 from [Apple](https://opensource.apple.com/source/mDNSResponder/mDNSResponder-544/mDNSShared/dns_sd.h.auto.html).   
diff --git a/README.txt b/README.txt
index 60ca67f..aaa2905 100644
--- a/README.txt
+++ b/README.txt
@@ -1290,7 +1290,10 @@ that your network **does not have a running Bonjour/zeroconf DNS-SD
 server.** Before v1.60, UxPlay used to stall silently if DNS-SD service
 registration failed, but now stops with an error message returned by the
 DNSServiceRegister function: kDNSServiceErr_Unknown if no DNS-SD server
-was found: other mDNS error codes are in the range FFFE FF00 (-65792) to
+was found. (A NixOS user found that in NixOS, this error can also occur
+if avahi-daemon service IS running with publishing enabled, but reports
+"the error disappeared on NixOS by setting services.avahi.openFirewall
+to true".) Other mDNS error codes are in the range FFFE FF00 (-65792) to
 FFFE FFFF (-65537), and are listed in the dnssd.h file. An older version
 of this (the one used by avahi) is found
 [here](https://github.com/lathiat/avahi/blob/master/avahi-compat-libdns_sd/dns_sd.h).