diff --git a/sys/dev/dev_dmem.pas b/sys/dev/dev_dmem.pas
index 131025e1..54ceec4f 100644
--- a/sys/dev/dev_dmem.pas
+++ b/sys/dev/dev_dmem.pas
@@ -285,7 +285,7 @@ begin
 
  ofs:=offset^;
 
- if (ofs > -1) and (size <= $5000000000 - ofs) then
+ if (ofs > -1) and (size <= max_valid_dmem - ofs) then
  begin
   //
  end else
diff --git a/sys/kern/kern_dmem.pas b/sys/kern/kern_dmem.pas
index 34580e42..c5e2433c 100644
--- a/sys/kern/kern_dmem.pas
+++ b/sys/kern/kern_dmem.pas
@@ -216,7 +216,7 @@ begin
  Result:=0;
  addr^:=0;
 
- if (((phaddr shr 36) > 4) or ((max_valid - phaddr) < length)) then
+ if (((phaddr shr 36) > 4) or ((max_valid_dmem - phaddr) < length)) then
  begin
   Exit(EACCES);
  end;
diff --git a/sys/vm/dmem_map.pas b/sys/vm/dmem_map.pas
index 37d6255e..eb9ded1f 100644
--- a/sys/vm/dmem_map.pas
+++ b/sys/vm/dmem_map.pas
@@ -30,7 +30,7 @@ Const
  SCE_KERNEL_UC_GARLIC_VOLATILE    = 8;
  SCE_KERNEL_UC_GARLIC_NONVOLATILE = 9;
 
- max_valid=QWORD($5000000000);
+ max_valid_dmem=QWORD($5000000000);
 
 type
  pp_dmem_map_entry=^p_dmem_map_entry;
@@ -620,10 +620,10 @@ begin
  if (align<PAGE_SIZE) then align:=PAGE_SIZE;
 
  start:=(not (start shr 63)) and start;
- if (start>max_valid) then start:=max_valid;
+ if (start>max_valid_dmem) then start:=max_valid_dmem;
 
  __end:=(not (__end shr 63)) and __end;
- if (__end>max_valid) then __end:=max_valid;
+ if (__end>max_valid_dmem) then __end:=max_valid_dmem;
 
  start:=AlignUp(start,align);
 
@@ -863,7 +863,7 @@ begin
 
  start:=(not (start shr 63)) and start;
 
- if (__end>max_valid) then __end:=max_valid;
+ if (__end>max_valid_dmem) then __end:=max_valid_dmem;
 
  if (__end <= start) then
  begin
@@ -1001,12 +1001,12 @@ begin
   Exit(EINVAL);
  end;
 
- if (Int64(start) > Int64($4fffffffff)) then
+ if (Int64(start) >= max_valid_dmem) then
  begin
   Exit(0);
  end;
 
- offset:=QWORD($5000000000) - start;
+ offset:=max_valid_dmem - start;
 
  if (Int64(len) < Int64(offset)) then
  begin