diff --git a/gdbstub/user-target.c b/gdbstub/user-target.c
index c4bba4c72c..b760beb0fc 100644
--- a/gdbstub/user-target.c
+++ b/gdbstub/user-target.c
@@ -316,9 +316,9 @@ void gdb_handle_v_file_open(GArray *params, void *user_ctx)
     int fd = open(filename, flags, mode);
 #endif
     if (fd < 0) {
-        g_string_printf(gdbserver_state.str_buf, "F-1,%d", errno);
+        g_string_printf(gdbserver_state.str_buf, "F-1,%x", errno);
     } else {
-        g_string_printf(gdbserver_state.str_buf, "F%d", fd);
+        g_string_printf(gdbserver_state.str_buf, "F%x", fd);
     }
     gdb_put_strbuf();
 }
@@ -328,7 +328,7 @@ void gdb_handle_v_file_close(GArray *params, void *user_ctx)
     int fd = get_param(params, 0)->val_ul;
 
     if (close(fd) == -1) {
-        g_string_printf(gdbserver_state.str_buf, "F-1,%d", errno);
+        g_string_printf(gdbserver_state.str_buf, "F-1,%x", errno);
         gdb_put_strbuf();
         return;
     }
@@ -351,7 +351,7 @@ void gdb_handle_v_file_pread(GArray *params, void *user_ctx)
 
     ssize_t n = pread(fd, buf, bufsiz, offset);
     if (n < 0) {
-        g_string_printf(gdbserver_state.str_buf, "F-1,%d", errno);
+        g_string_printf(gdbserver_state.str_buf, "F-1,%x", errno);
         gdb_put_strbuf();
         return;
     }
@@ -374,7 +374,7 @@ void gdb_handle_v_file_readlink(GArray *params, void *user_ctx)
     ssize_t n = readlink(filename, buf, BUFSIZ);
 #endif
     if (n < 0) {
-        g_string_printf(gdbserver_state.str_buf, "F-1,%d", errno);
+        g_string_printf(gdbserver_state.str_buf, "F-1,%x", errno);
         gdb_put_strbuf();
         return;
     }