diff --git a/src/ca/client/udpiiu.cpp b/src/ca/client/udpiiu.cpp
index 73d4ee4cb..00d764d7c 100644
--- a/src/ca/client/udpiiu.cpp
+++ b/src/ca/client/udpiiu.cpp
@@ -193,7 +193,7 @@ udpiiu::udpiiu (
 
 #ifdef IP_MULTICAST_TTL
     {
-        int ttl;
+        osiSockOptMcastTTL_t ttl;
         long val;
         if(envGetLongConfigParam(&EPICS_CA_MCAST_TTL, &val))
             val =1;
diff --git a/src/ioc/rsrv/caservertask.c b/src/ioc/rsrv/caservertask.c
index 3a493e7f1..ea9e7b59a 100644
--- a/src/ioc/rsrv/caservertask.c
+++ b/src/ioc/rsrv/caservertask.c
@@ -324,7 +324,7 @@ void rsrv_build_addr_lists(void)
 
 #ifdef IP_MULTICAST_TTL
     {
-        int ttl;
+        osiSockOptMcastTTL_t ttl;
         long val;
         if(envGetLongConfigParam(&EPICS_CA_MCAST_TTL, &val))
             val =1;
diff --git a/src/libCom/osi/os/Darwin/osdSock.h b/src/libCom/osi/os/Darwin/osdSock.h
index e7c344062..0122d16de 100644
--- a/src/libCom/osi/os/Darwin/osdSock.h
+++ b/src/libCom/osi/os/Darwin/osdSock.h
@@ -32,6 +32,7 @@ typedef int                     SOCKET;
 typedef int osiSockIoctl_t;
 typedef socklen_t osiSocklen_t;
 typedef int osiSockOptMcastLoop_t;
+typedef unsigned char osiSockOptMcastTTL_t;
 
 #define FD_IN_FDSET(FD) ((FD)<FD_SETSIZE)
 
diff --git a/src/libCom/osi/os/Linux/osdSock.h b/src/libCom/osi/os/Linux/osdSock.h
index 7164a54ee..89cca06d9 100644
--- a/src/libCom/osi/os/Linux/osdSock.h
+++ b/src/libCom/osi/os/Linux/osdSock.h
@@ -36,6 +36,7 @@ typedef int                     SOCKET;
 typedef int osiSockIoctl_t;
 typedef socklen_t osiSocklen_t;
 typedef int osiSockOptMcastLoop_t;
+typedef int osiSockOptMcastTTL_t;
 
 #define FD_IN_FDSET(FD) ((FD)<FD_SETSIZE)
 
diff --git a/src/libCom/osi/os/RTEMS/osdSock.h b/src/libCom/osi/os/RTEMS/osdSock.h
index 6177c3033..ec43b72ef 100644
--- a/src/libCom/osi/os/RTEMS/osdSock.h
+++ b/src/libCom/osi/os/RTEMS/osdSock.h
@@ -43,6 +43,7 @@ typedef int                     SOCKET;
 typedef int osiSockIoctl_t;
 typedef socklen_t osiSocklen_t;
 typedef char osiSockOptMcastLoop_t;
+typedef unsigned char osiSockOptMcastTTL_t;
 
 #define FD_IN_FDSET(FD) ((FD)<FD_SETSIZE)
 
diff --git a/src/libCom/osi/os/WIN32/osdSock.h b/src/libCom/osi/os/WIN32/osdSock.h
index 2ff23c4a6..c1bc1d9b1 100644
--- a/src/libCom/osi/os/WIN32/osdSock.h
+++ b/src/libCom/osi/os/WIN32/osdSock.h
@@ -29,6 +29,7 @@
 typedef u_long FAR osiSockIoctl_t;
 typedef int osiSocklen_t;
 typedef BOOL osiSockOptMcastLoop_t;
+typedef DWORD osiSockOptMcastTTL_t;
 
 #ifndef SHUT_RD
 #   define SHUT_RD SD_RECEIVE
diff --git a/src/libCom/osi/os/cygwin32/osdSock.h b/src/libCom/osi/os/cygwin32/osdSock.h
index 75288c865..123f2404f 100644
--- a/src/libCom/osi/os/cygwin32/osdSock.h
+++ b/src/libCom/osi/os/cygwin32/osdSock.h
@@ -35,6 +35,8 @@ typedef int                     SOCKET;
 typedef int osiSockIoctl_t;
 typedef int osiSocklen_t;
 typedef int osiSockOptMcastLoop_t;
+typedef int osiSockOptMcastTTL_t;
+
 #define FD_IN_FDSET(FD) ((FD)<FD_SETSIZE&&(FD)>=0)
 #ifndef SHUT_RD
 #define SHUT_RD 0
diff --git a/src/libCom/osi/os/freebsd/osdSock.h b/src/libCom/osi/os/freebsd/osdSock.h
index b402ec120..2e6951399 100644
--- a/src/libCom/osi/os/freebsd/osdSock.h
+++ b/src/libCom/osi/os/freebsd/osdSock.h
@@ -37,6 +37,7 @@ typedef int                     SOCKET;
 typedef int osiSockIoctl_t;
 typedef socklen_t osiSocklen_t;
 typedef int osiSockOptMcastLoop_t;
+typedef unsigned char osiSockOptMcastTTL_t;
 
 #define FD_IN_FDSET(FD) ((FD)<FD_SETSIZE)
 
diff --git a/src/libCom/osi/os/iOS/osdSock.h b/src/libCom/osi/os/iOS/osdSock.h
index 08849a8d8..fa860b349 100644
--- a/src/libCom/osi/os/iOS/osdSock.h
+++ b/src/libCom/osi/os/iOS/osdSock.h
@@ -33,6 +33,7 @@ typedef int                     SOCKET;
 typedef int osiSockIoctl_t;
 typedef socklen_t osiSocklen_t;
 typedef int osiSockOptMcastLoop_t;
+typedef unsigned char osiSockOptMcastTTL_t;
 
 #define FD_IN_FDSET(FD) ((FD)<FD_SETSIZE)
 
diff --git a/src/libCom/osi/os/solaris/osdSock.h b/src/libCom/osi/os/solaris/osdSock.h
index 96ea2a983..adf3d9bad 100644
--- a/src/libCom/osi/os/solaris/osdSock.h
+++ b/src/libCom/osi/os/solaris/osdSock.h
@@ -43,6 +43,7 @@ typedef int osiSockIoctl_t;
     typedef int osiSocklen_t;
 #endif
 typedef char osiSockOptMcastLoop_t;
+typedef unsigned char osiSockOptMcastTTL_t;
 
 #define DOES_NOT_ACCEPT_ZERO_LENGTH_UDP
 
diff --git a/src/libCom/osi/os/vxWorks/osdSock.h b/src/libCom/osi/os/vxWorks/osdSock.h
index d949b25f1..272371523 100644
--- a/src/libCom/osi/os/vxWorks/osdSock.h
+++ b/src/libCom/osi/os/vxWorks/osdSock.h
@@ -66,6 +66,7 @@ typedef int                     SOCKET;
 typedef int osiSockIoctl_t;
 typedef int osiSocklen_t;
 typedef int osiSockOptMcastLoop_t;
+typedef char osiSockOptMcastTTL_t;
 
 #define FD_IN_FDSET(FD) ((FD)<FD_SETSIZE&&(FD)>=0)