diff --git a/components/lazutils/masks.pas b/components/lazutils/masks.pas
index 77d14d1f4a..7c3a6fe466 100644
--- a/components/lazutils/masks.pas
+++ b/components/lazutils/masks.pas
@@ -1408,10 +1408,16 @@ var
   lFileNameMask: String;
   lExtensionMask: String;
   lModifiedMask: String;
+  ZeroPos: SizeInt;
 
 begin
   lModifiedMask:=fWindowsMask;
 
+  //We cannot have #0 in the mask,since we use it internally
+  ZeroPos:=Pos(#0, fWindowsMask);
+  if ZeroPos>0 then
+    Exception_InvalidCharMask('NullCharacter', ZeroPos);
+
   // Quirk "blah.*" = "blah*"
   if wqAnyExtension in fWindowsQuirkAllowed then begin
     if RightStr(lModifiedMask,3)='*.*' then begin
@@ -1448,7 +1454,7 @@ begin
     end;
   end;
 
-  }
+
   // Quirk "file???.ab?" matches "file1.ab1" and "file123.ab"
   if wqFilenameEnd in fWindowsQuirkAllowed then begin
     lFileNameMask:=OptionalQMarksAtEnd(lFileNameMask);