diff --git a/gui/cfg_edit.pas b/gui/cfg_edit.pas
index 368eb259..90b78175 100644
--- a/gui/cfg_edit.pas
+++ b/gui/cfg_edit.pas
@@ -217,6 +217,8 @@ begin
  if (src=nil) then Exit;
 
  i:=src.ItemIndex;
+ if (i=-1) then Exit;
+
  ptr:=PVkPhysicalDeviceProperties(src.Items.Objects[i]);
 
  if (ptr=nil) then Exit;
diff --git a/gui/game_run.pas b/gui/game_run.pas
index 4b9a0b95..ca6a9377 100644
--- a/gui/game_run.pas
+++ b/gui/game_run.pas
@@ -121,7 +121,11 @@ end;
 
 Destructor TGameProcessSimple.Destroy;
 begin
- thread_dec_ref(Ftd);
+ if (Ftd<>nil) then
+ begin
+  thread_dec_ref(Ftd);
+  Ftd:=nil;
+ end;
  inherited;
 end;
 
diff --git a/sys/kern/kern_thread.pas b/sys/kern/kern_thread.pas
index d718d4e3..973a4644 100644
--- a/sys/kern/kern_thread.pas
+++ b/sys/kern/kern_thread.pas
@@ -679,6 +679,7 @@ begin
 
  if (n<>0) then
  begin
+  Writeln(StdErr,'failed cpu_thread_create:0x',HexStr(n,8));
   thread_free(newtd);
   Exit(EINVAL);
  end;
diff --git a/sys/md/md_thread.pas b/sys/md/md_thread.pas
index 7af2aae4..9a3f3392 100644
--- a/sys/md/md_thread.pas
+++ b/sys/md/md_thread.pas
@@ -325,7 +325,7 @@ begin
    Result:=0;
   end else
   begin
-   Result:=-1;
+   Result:=GetLastError;
   end;
  {$ENDIF}