diff --git a/src/compositor-fbdev.c b/src/compositor-fbdev.c
index a5c79476..81281d04 100644
--- a/src/compositor-fbdev.c
+++ b/src/compositor-fbdev.c
@@ -337,7 +337,7 @@ fbdev_query_screen_info(struct fbdev_output *output, int fd,
 
 	info->buffer_length = fixinfo.smem_len;
 	info->line_length = fixinfo.line_length;
-	strncpy(info->id, fixinfo.id, sizeof(info->id) / sizeof(*info->id));
+	strncpy(info->id, fixinfo.id, sizeof(info->id));
 
 	info->pixel_format = calculate_pixman_format(&varinfo, &fixinfo);
 	info->refresh_rate = calculate_refresh_rate(&varinfo);