diff --git a/t/t1007-hash-object.sh b/t/t1007-hash-object.sh
index a37753047e..7099d33508 100755
--- a/t/t1007-hash-object.sh
+++ b/t/t1007-hash-object.sh
@@ -199,10 +199,6 @@ test_expect_success 'too-short tree' '
 	test_i18ngrep "too-short tree object" err
 '
 
-hex2oct() {
-    perl -ne 'printf "\\%03o", hex for /../g'
-}
-
 test_expect_success 'malformed mode in tree' '
 	hex_sha1=$(echo foo | git hash-object --stdin -w) &&
 	bin_sha1=$(echo $hex_sha1 | hex2oct) &&
diff --git a/t/t1450-fsck.sh b/t/t1450-fsck.sh
index c61f972141..0b4d874de6 100755
--- a/t/t1450-fsck.sh
+++ b/t/t1450-fsck.sh
@@ -256,10 +256,6 @@ test_expect_success 'unparseable tree object' '
 	test_i18ngrep ! "fatal: empty filename in tree entry" out
 '
 
-hex2oct() {
-	perl -ne 'printf "\\%03o", hex for /../g'
-}
-
 test_expect_success 'tree entry with type mismatch' '
 	test_when_finished "remove_object \$blob" &&
 	test_when_finished "remove_object \$tree" &&
diff --git a/t/t5601-clone.sh b/t/t5601-clone.sh
index d6948cbdab..3f49943010 100755
--- a/t/t5601-clone.sh
+++ b/t/t5601-clone.sh
@@ -611,10 +611,6 @@ test_expect_success 'GIT_TRACE_PACKFILE produces a usable pack' '
 	git -C replay.git index-pack -v --stdin <tmp.pack
 '
 
-hex2oct () {
-	perl -ne 'printf "\\%03o", hex for /../g'
-}
-
 test_expect_success 'clone on case-insensitive fs' '
 	git init icasefs &&
 	(
diff --git a/t/test-lib-functions.sh b/t/test-lib-functions.sh
index 80402a428f..349eabe851 100644
--- a/t/test-lib-functions.sh
+++ b/t/test-lib-functions.sh
@@ -1202,6 +1202,12 @@ depacketize () {
 	'
 }
 
+# Converts base-16 data into base-8. The output is given as a sequence of
+# escaped octals, suitable for consumption by 'printf'.
+hex2oct () {
+	perl -ne 'printf "\\%03o", hex for /../g'
+}
+
 # Set the hash algorithm in use to $1.  Only useful when testing the testsuite.
 test_set_hash () {
 	test_hash_algo="$1"