diff --git a/board/ACube/common/sys_dep.c b/board/ACube/common/sys_dep.c
index ff58686..3057323 100644
--- a/board/ACube/common/sys_dep.c
+++ b/board/ACube/common/sys_dep.c
@@ -149,7 +149,7 @@
   const char ** opt_list;
   struct dev_access_entry * dae_found;
   //printf("entered start_unit_scan\n");
-
+  if (!scan_list || !blocksize) return NULL;
   //floppy_like_an_hd.block_read = internal_floppy_block_read;
 
   /* This routine builds a list of scan handles from the env-vars passed in scan_list. */