diff --git a/t/t5000-tar-tree.sh b/t/t5000-tar-tree.sh
index d01bbdc968..4b68bbafbe 100755
--- a/t/t5000-tar-tree.sh
+++ b/t/t5000-tar-tree.sh
@@ -101,7 +101,7 @@ test_expect_success \
      ten=0123456789 && hundred=$ten$ten$ten$ten$ten$ten$ten$ten$ten$ten &&
      echo long filename >a/four$hundred &&
      mkdir a/bin &&
-     cp /bin/sh a/bin &&
+     test-genrandom "frotz" 500000 >a/bin/sh &&
      printf "A\$Format:%s\$O" "$SUBSTFORMAT" >a/substfile1 &&
      printf "A not substituted O" >a/substfile2 &&
      if test_have_prereq SYMLINKS; then