diff --git a/t/t0021-conversion.sh b/t/t0021-conversion.sh
index 033b00a364..7b9a0ca877 100755
--- a/t/t0021-conversion.sh
+++ b/t/t0021-conversion.sh
@@ -296,7 +296,7 @@ test_expect_success 'filter that does not read is fine' '
 	test_cmp expect actual
 '
 
-test_expect_success EXPENSIVE 'filter large file' '
+test_expect_success EXPENSIVE,SIZE_T_IS_64BIT 'filter large file' '
 	test_config filter.largefile.smudge cat &&
 	test_config filter.largefile.clean cat &&
 	test_seq -f "%1048576d" 1 2048 >2GB &&