diff --git a/t/t5301-sliding-window.sh b/t/t5301-sliding-window.sh
index 9a6d6aceac..073ac0c6f9 100755
--- a/t/t5301-sliding-window.sh
+++ b/t/t5301-sliding-window.sh
@@ -6,10 +6,6 @@
 test_description='mmap sliding window tests'
 . ./test-lib.sh
 
-dd () {
-	perl -e 'print pack("C", rand(256)) foreach 0 .. 32767'
-}
-
 test_expect_success \
     'setup' \
     'rm -f .git/index*