diff --git a/t/t5300-pack-object.sh b/t/t5300-pack-object.sh
index ccfc64c6ee..e2aa254eae 100755
--- a/t/t5300-pack-object.sh
+++ b/t/t5300-pack-object.sh
@@ -13,11 +13,10 @@ TRASH=`pwd`
 test_expect_success \
     'setup' \
     'rm -f .git/index*
-     for i in a b c
-     do
-	     dd if=/dev/zero bs=4k count=1 | perl -pe "y/\\000/$i/" >$i &&
-	     git update-index --add $i || return 1
-     done &&
+     perl -e "print \"a\" x 4096;" > a &&
+     perl -e "print \"b\" x 4096;" > b &&
+     perl -e "print \"c\" x 4096;" > c &&
+     git update-index --add a b c &&
      cat c >d && echo foo >>d && git update-index --add d &&
      tree=`git write-tree` &&
      commit=`git commit-tree $tree </dev/null` && {
@@ -221,7 +220,7 @@ test_expect_success \
 test_expect_success \
     'verify-pack catches a corrupted pack signature' \
     'cat test-1-${packname_1}.pack >test-3.pack &&
-     dd if=/dev/zero of=test-3.pack count=1 bs=1 conv=notrunc seek=2 &&
+     echo | dd of=test-3.pack count=1 bs=1 conv=notrunc seek=2 &&
      if git verify-pack test-3.idx
      then false
      else :;
@@ -230,7 +229,7 @@ test_expect_success \
 test_expect_success \
     'verify-pack catches a corrupted pack version' \
     'cat test-1-${packname_1}.pack >test-3.pack &&
-     dd if=/dev/zero of=test-3.pack count=1 bs=1 conv=notrunc seek=7 &&
+     echo | dd of=test-3.pack count=1 bs=1 conv=notrunc seek=7 &&
      if git verify-pack test-3.idx
      then false
      else :;
@@ -239,7 +238,7 @@ test_expect_success \
 test_expect_success \
     'verify-pack catches a corrupted type/size of the 1st packed object data' \
     'cat test-1-${packname_1}.pack >test-3.pack &&
-     dd if=/dev/zero of=test-3.pack count=1 bs=1 conv=notrunc seek=12 &&
+     echo | dd of=test-3.pack count=1 bs=1 conv=notrunc seek=12 &&
      if git verify-pack test-3.idx
      then false
      else :;
@@ -250,7 +249,7 @@ test_expect_success \
     'l=`wc -c <test-3.idx` &&
      l=`expr $l - 20` &&
      cat test-1-${packname_1}.pack >test-3.pack &&
-     dd if=/dev/zero of=test-3.idx count=20 bs=1 conv=notrunc seek=$l &&
+     printf "%20s" "" | dd of=test-3.idx count=20 bs=1 conv=notrunc seek=$l &&
      if git verify-pack test-3.pack
      then false
      else :;
diff --git a/t/t5302-pack-index.sh b/t/t5302-pack-index.sh
index e6f70d474f..77982cdeac 100755
--- a/t/t5302-pack-index.sh
+++ b/t/t5302-pack-index.sh
@@ -208,7 +208,7 @@ test_expect_success \
      obj=`git hash-object file_001` &&
      nr=`index_obj_nr ".git/objects/pack/pack-${pack1}.idx" $obj` &&
      chmod +w ".git/objects/pack/pack-${pack1}.idx" &&
-     dd if=/dev/zero of=".git/objects/pack/pack-${pack1}.idx" conv=notrunc \
+     printf xxxx | dd of=".git/objects/pack/pack-${pack1}.idx" conv=notrunc \
         bs=1 count=4 seek=$((8 + 256 * 4 + `wc -l <obj-list` * 20 + $nr * 4)) &&
      ( while read obj
        do git cat-file -p $obj >/dev/null || exit 1
diff --git a/t/t5303-pack-corruption-resilience.sh b/t/t5303-pack-corruption-resilience.sh
index d4e30fc43c..5132d41309 100755
--- a/t/t5303-pack-corruption-resilience.sh
+++ b/t/t5303-pack-corruption-resilience.sh
@@ -55,6 +55,8 @@ do_corrupt_object() {
     test_must_fail git verify-pack ${pack}.pack
 }
 
+printf '\0' > zero
+
 test_expect_success \
     'initial setup validation' \
     'create_test_files &&
@@ -66,7 +68,7 @@ test_expect_success \
 
 test_expect_success \
     'create corruption in header of first object' \
-    'do_corrupt_object $blob_1 0 < /dev/zero &&
+    'do_corrupt_object $blob_1 0 < zero &&
      test_must_fail git cat-file blob $blob_1 > /dev/null &&
      test_must_fail git cat-file blob $blob_2 > /dev/null &&
      test_must_fail git cat-file blob $blob_3 > /dev/null'
@@ -125,7 +127,7 @@ test_expect_success \
     'create corruption in header of first delta' \
     'create_new_pack &&
      git prune-packed &&
-     do_corrupt_object $blob_2 0 < /dev/zero &&
+     do_corrupt_object $blob_2 0 < zero &&
      git cat-file blob $blob_1 > /dev/null &&
      test_must_fail git cat-file blob $blob_2 > /dev/null &&
      test_must_fail git cat-file blob $blob_3 > /dev/null'
@@ -180,7 +182,7 @@ test_expect_success \
     'corruption in delta base reference of first delta (OBJ_REF_DELTA)' \
     'create_new_pack &&
      git prune-packed &&
-     do_corrupt_object $blob_2 2 < /dev/zero &&
+     do_corrupt_object $blob_2 2 < zero &&
      git cat-file blob $blob_1 > /dev/null &&
      test_must_fail git cat-file blob $blob_2 > /dev/null &&
      test_must_fail git cat-file blob $blob_3 > /dev/null'
@@ -207,7 +209,7 @@ test_expect_success \
     'corruption #0 in delta base reference of first delta (OBJ_OFS_DELTA)' \
     'create_new_pack --delta-base-offset &&
      git prune-packed &&
-     do_corrupt_object $blob_2 2 < /dev/zero &&
+     do_corrupt_object $blob_2 2 < zero &&
      git cat-file blob $blob_1 > /dev/null &&
      test_must_fail git cat-file blob $blob_2 > /dev/null &&
      test_must_fail git cat-file blob $blob_3 > /dev/null'
@@ -259,7 +261,7 @@ test_expect_success \
 
 test_expect_success \
     '... and a redundant pack allows for full recovery too' \
-    'do_corrupt_object $blob_2 2 < /dev/zero &&
+    'do_corrupt_object $blob_2 2 < zero &&
      git cat-file blob $blob_1 > /dev/null &&
      test_must_fail git cat-file blob $blob_2 > /dev/null &&
      test_must_fail git cat-file blob $blob_3 > /dev/null &&