diff --git a/ext/socket/socket.c b/ext/socket/socket.c
index 175db9b560..7fe4e3defa 100644
--- a/ext/socket/socket.c
+++ b/ext/socket/socket.c
@@ -766,9 +766,9 @@ bsock_do_not_rev_lookup_set(VALUE self, VALUE val)
     return val;
 }
 
-NORETURN(static void raise_socket_error(char *, int));
+NORETURN(static void raise_socket_error(const char *, int));
 static void
-raise_socket_error(char *reason, int error)
+raise_socket_error(const char *reason, int error)
 {
 #ifdef EAI_SYSTEM
     if (error == EAI_SYSTEM) rb_sys_fail(reason);
@@ -1239,7 +1239,7 @@ init_inetsock_internal(struct inetsock_arg *arg)
     int type = arg->type;
     struct addrinfo *res;
     int fd, status = 0;
-    char *syscall;
+    const char *syscall;
 
     arg->remote.res = sock_addrinfo(arg->remote.host, arg->remote.serv, SOCK_STREAM,
 				    (type == INET_SERVER) ? AI_PASSIVE : 0);
@@ -1870,7 +1870,7 @@ unix_init(VALUE sock, VALUE path)
     return init_unixsock(sock, path, 0);
 }
 
-static char*
+static const char*
 unixpath(struct sockaddr_un *sockaddr, socklen_t len)
 {
     if (sockaddr->sun_path < (char*)sockaddr + len)
@@ -3462,7 +3462,7 @@ static VALUE
 sock_s_unpack_sockaddr_un(VALUE self, VALUE addr)
 {
     struct sockaddr_un * sockaddr;
-    char *sun_path;
+    const char *sun_path;
     VALUE path;
 
     sockaddr = (struct sockaddr_un*)StringValuePtr(addr);
@@ -3488,7 +3488,7 @@ sock_s_unpack_sockaddr_un(VALUE self, VALUE addr)
 static VALUE mConst;
 
 static void
-sock_define_const(char *name, int value)
+sock_define_const(const char *name, int value)
 {
     rb_define_const(rb_cSocket, name, INT2FIX(value));
     rb_define_const(mConst, name, INT2FIX(value));