diff --git a/builtin/pack-objects.c b/builtin/pack-objects.c
index 6d13cd3e1a..ea7a5b3ba5 100644
--- a/builtin/pack-objects.c
+++ b/builtin/pack-objects.c
@@ -3871,6 +3871,8 @@ int cmd_pack_objects(int argc, const char **argv, const char *prefix)
 			(1U << OE_Z_DELTA_BITS) - 1);
 		cache_max_small_delta_size = (1U << OE_Z_DELTA_BITS) - 1;
 	}
+	if (window < 0)
+		window = 0;
 
 	strvec_push(&rp, "pack-objects");
 	if (thin) {
diff --git a/t/t5300-pack-object.sh b/t/t5300-pack-object.sh
index 887e2d8d88..5c5e53f0be 100755
--- a/t/t5300-pack-object.sh
+++ b/t/t5300-pack-object.sh
@@ -613,4 +613,9 @@ test_expect_success '--stdin-packs with broken links' '
 	)
 '
 
+test_expect_success 'negative window clamps to 0' '
+	git pack-objects --progress --window=-1 neg-window <obj-list 2>stderr &&
+	check_deltas stderr = 0
+'
+
 test_done