diff --git a/bin/CP b/bin/CP
index 6b800e5c..8082b34d 100755
--- a/bin/CP
+++ b/bin/CP
@@ -4,12 +4,18 @@
 # so I converted CP back to perl. :)
 
 use File::Basename ;
+use Cwd ;
 use Cwd 'abs_path';
 
 $trick_bin = dirname(abs_path($0)) ;
 $trick_home = dirname($trick_bin) ;
 
 if ( -f "S_define" ) {
+    if ( not -w "." ) {
+        print getcwd() , " is not writable\n" ;
+        print "CP aborted\n" ;
+        exit 1 ;
+    }
     unlink "Makefile_sim", "makefile" ;
     $makefile_text = do { local $/; <main::DATA> } ;
     $makefile_text =~ s/SUB_TRICK_HOME/$trick_home/ ;