diff --git a/dlls/ntdll/file.c b/dlls/ntdll/file.c
index 7b170a82995..5d397cc1339 100644
--- a/dlls/ntdll/file.c
+++ b/dlls/ntdll/file.c
@@ -1350,12 +1350,29 @@ NTSTATUS WINAPI NtQueryInformationFile( HANDLE hFile, PIO_STATUS_BLOCK io,
                 {
                     info->MaximumMessageSize = reply->max_msgsize;
                     info->MailslotQuota = 0;
-                    info->NextMessageSize = reply->next_msgsize;
-                    info->MessagesAvailable = reply->msg_count;
+                    info->NextMessageSize = 0;
+                    info->MessagesAvailable = 0;
                     info->ReadTimeout.QuadPart = reply->read_timeout * -10000;
                 }
             }
             SERVER_END_REQ;
+            if (!io->u.Status)
+            {
+                ULONG size = info->MaximumMessageSize ? info->MaximumMessageSize : 0x10000;
+                char *tmpbuf = RtlAllocateHeap( GetProcessHeap(), 0, size );
+                if (tmpbuf)
+                {
+                    int fd, needs_close;
+                    if (!server_get_unix_fd( hFile, FILE_READ_DATA, &fd, &needs_close, NULL ))
+                    {
+                        int res = recv( fd, tmpbuf, size, MSG_PEEK );
+                        info->MessagesAvailable = (res > 0);
+                        info->NextMessageSize = (res >= 0) ? res : MAILSLOT_NO_MESSAGE;
+                        if (needs_close) close( fd );
+                    }
+                    RtlFreeHeap( GetProcessHeap(), 0, tmpbuf );
+                }
+            }
         }
         break;
     case FilePipeLocalInformation:
diff --git a/include/wine/server_protocol.h b/include/wine/server_protocol.h
index 577c797183a..09b8906cf65 100644
--- a/include/wine/server_protocol.h
+++ b/include/wine/server_protocol.h
@@ -3666,8 +3666,6 @@ struct set_mailslot_info_reply
     struct reply_header __header;
     unsigned int   max_msgsize;
     int            read_timeout;
-    unsigned int   msg_count;
-    unsigned int   next_msgsize;
 };
 #define MAILSLOT_SET_READ_TIMEOUT  1
 
@@ -4406,6 +4404,6 @@ union generic_reply
     struct query_symlink_reply query_symlink_reply;
 };
 
-#define SERVER_PROTOCOL_VERSION 258
+#define SERVER_PROTOCOL_VERSION 259
 
 #endif /* __WINE_WINE_SERVER_PROTOCOL_H */
diff --git a/server/mailslot.c b/server/mailslot.c
index 7015f41358a..578f75131c6 100644
--- a/server/mailslot.c
+++ b/server/mailslot.c
@@ -212,16 +212,6 @@ static int mailslot_message_count(struct mailslot *mailslot)
     return (poll( &pfd, 1, 0 ) == 1) ? 1 : 0;
 }
 
-static int mailslot_next_msg_size( struct mailslot *mailslot )
-{
-    int size, fd;
-
-    size = 0;
-    fd = get_unix_fd( mailslot->fd );
-    ioctl( fd, FIONREAD, &size );
-    return size;
-}
-
 static int mailslot_get_info( struct fd *fd )
 {
     struct mailslot *mailslot = get_fd_user( fd );
@@ -541,14 +531,6 @@ DECL_HANDLER(set_mailslot_info)
             mailslot->read_timeout = req->read_timeout;
         reply->max_msgsize = mailslot->max_msgsize;
         reply->read_timeout = mailslot->read_timeout;
-        reply->msg_count = mailslot_message_count(mailslot);
-
-        /* get the size of the next message */
-        if (reply->msg_count)
-            reply->next_msgsize = mailslot_next_msg_size(mailslot);
-        else
-            reply->next_msgsize = MAILSLOT_NO_MESSAGE;
-
         release_object( mailslot );
     }
 }
diff --git a/server/protocol.def b/server/protocol.def
index a4a2376d66c..192b8a39cfb 100644
--- a/server/protocol.def
+++ b/server/protocol.def
@@ -2578,8 +2578,6 @@ enum message_type
 @REPLY
     unsigned int   max_msgsize;
     int            read_timeout;
-    unsigned int   msg_count;
-    unsigned int   next_msgsize;
 @END
 #define MAILSLOT_SET_READ_TIMEOUT  1
 
diff --git a/server/trace.c b/server/trace.c
index 9931ea0ab86..50268f94222 100644
--- a/server/trace.c
+++ b/server/trace.c
@@ -3186,9 +3186,7 @@ static void dump_set_mailslot_info_request( const struct set_mailslot_info_reque
 static void dump_set_mailslot_info_reply( const struct set_mailslot_info_reply *req )
 {
     fprintf( stderr, " max_msgsize=%08x,", req->max_msgsize );
-    fprintf( stderr, " read_timeout=%d,", req->read_timeout );
-    fprintf( stderr, " msg_count=%08x,", req->msg_count );
-    fprintf( stderr, " next_msgsize=%08x", req->next_msgsize );
+    fprintf( stderr, " read_timeout=%d", req->read_timeout );
 }
 
 static void dump_create_directory_request( const struct create_directory_request *req )