diff --git a/packages/rtl-extra/src/os2commn/sockets.pp b/packages/rtl-extra/src/os2commn/sockets.pp
index 99bf16c378..01d4bb1e94 100644
--- a/packages/rtl-extra/src/os2commn/sockets.pp
+++ b/packages/rtl-extra/src/os2commn/sockets.pp
@@ -108,6 +108,7 @@ const
   EsockENOTSOCK = SOCENOTSOCK;
   EsockEPROTONOSUPPORT = SOCEPROTONOSUPPORT;
   EsockEWOULDBLOCK = SOCEWOULDBLOCK;
+  EsockADDRINUSE = SOCEADDRINUSE;
 
 
 (***************************************************************************)
diff --git a/packages/rtl-extra/src/unix/sockets.pp b/packages/rtl-extra/src/unix/sockets.pp
index 2888aea723..234afe3b89 100644
--- a/packages/rtl-extra/src/unix/sockets.pp
+++ b/packages/rtl-extra/src/unix/sockets.pp
@@ -59,7 +59,7 @@ const
 {$endif beos}
   EsockEPROTONOSUPPORT  = ESysEProtoNoSupport;
   EsockEWOULDBLOCK      = ESysEWouldBlock;
-
+  EsockADDRINUSE        = ESysEADDRINUSE;
 
 { unix socket specific functions }
 Procedure Str2UnixSockAddr(const addr:string;var t:TUnixSockAddr;var len:longint); deprecated;
diff --git a/packages/rtl-extra/src/win/sockets.pp b/packages/rtl-extra/src/win/sockets.pp
index 18e19a799d..561dbf8226 100644
--- a/packages/rtl-extra/src/win/sockets.pp
+++ b/packages/rtl-extra/src/win/sockets.pp
@@ -45,6 +45,7 @@ const
   EsockENOTSOCK        = WSAENOTSOCK;
   EsockEPROTONOSUPPORT = WSAEPROTONOSUPPORT;
   EsockEWOULDBLOCK     = WSAEWOULDBLOCK;
+  EsockADDRINUSE       = WSAEADDRINUSE;
 
   SHUT_RD          = SD_RECEIVE; // aliases so we are cross-platform
   SHUT_WR          = SD_SEND;