diff --git a/kernel/dsk.c b/kernel/dsk.c
index 654f8b9..70c4a8f 100644
--- a/kernel/dsk.c
+++ b/kernel/dsk.c
@@ -392,7 +392,7 @@ STATIC WORD getbpb(ddt * pddt)
   {
     /* copy default bpb to be sure that there is no bogus data */
     memcpy(pbpbarray, &pddt->ddt_defbpb, sizeof(bpb));
-    return S_DONE;
+    return 0;
   }
 
   pddt->ddt_descflags &= ~DF_NOACCESS;  /* set drive to accessible */
diff --git a/kernel/inthndlr.c b/kernel/inthndlr.c
index 5003512..089cbbc 100644
--- a/kernel/inthndlr.c
+++ b/kernel/inthndlr.c
@@ -1820,7 +1820,9 @@ VOID ASMCFUNC int2526_handler(WORD mode, struct int25regs FAR * r)
   else
     mode = DSKREADINT25;
 
-  drv = r->ax;
+  drv = r->ax & 0x7f; /* according to RBIL, some programs may try with */
+                      /* high bit of AL set, so mask it together with AH */
+                      /* otherwise we might access a non-existing unit */
 
   if (drv >= lastdrive)
   {