diff --git a/t/perf/p5311-pack-bitmaps-fetch.sh b/t/perf/p5311-pack-bitmaps-fetch.sh
index 426fab87e3293e..047efb995d647b 100755
--- a/t/perf/p5311-pack-bitmaps-fetch.sh
+++ b/t/perf/p5311-pack-bitmaps-fetch.sh
@@ -39,7 +39,7 @@ test_fetch_bitmaps () {
 		'
 
 		test_size "size   $title" '
-			wc -c <tmp.pack
+			test_file_size tmp.pack
 		'
 
 		test_perf "client $title (lookup=$1)" '
diff --git a/t/perf/p5332-multi-pack-reuse.sh b/t/perf/p5332-multi-pack-reuse.sh
index 5c6c575d62c64b..d1c89a8b7dbd5b 100755
--- a/t/perf/p5332-multi-pack-reuse.sh
+++ b/t/perf/p5332-multi-pack-reuse.sh
@@ -73,7 +73,7 @@ do
 		"
 
 		test_size "clone size for $nr_packs-pack scenario ($reuse-pack reuse)" '
-			wc -c <result
+			test_file_size result
 		'
 	done
 done