diff --git a/Documentation/git-backfill.txt b/Documentation/git-backfill.txt
index ecf2ac428cefb7..066ec6b161a22c 100644
--- a/Documentation/git-backfill.txt
+++ b/Documentation/git-backfill.txt
@@ -48,7 +48,8 @@ OPTIONS
 
 --[no-]sparse::
 	Only download objects if they appear at a path that matches the
-	current sparse-checkout.
+	current sparse-checkout. If the sparse-checkout feature is enabled,
+	then `--sparse` is assumed and can be disabled with `--no-sparse`.
 
 SEE ALSO
 --------
diff --git a/builtin/backfill.c b/builtin/backfill.c
index 949c93ad48d0c5..d37516b045036e 100644
--- a/builtin/backfill.c
+++ b/builtin/backfill.c
@@ -1,3 +1,5 @@
+#define USE_THE_REPOSITORY_VARIABLE /* for core_apply_sparse_checkout */
+
 #include "builtin.h"
 #include "git-compat-util.h"
 #include "config.h"
@@ -5,6 +7,7 @@
 #include "repository.h"
 #include "commit.h"
 #include "dir.h"
+#include "environment.h"
 #include "hex.h"
 #include "tree.h"
 #include "tree-walk.h"
@@ -136,5 +139,8 @@ int cmd_backfill(int argc, const char **argv, const char *prefix, struct reposit
 
 	repo_config(repo, git_default_config, NULL);
 
+	if (ctx.sparse < 0)
+		ctx.sparse = core_apply_sparse_checkout;
+
 	return do_backfill(&ctx);
 }
diff --git a/t/t5620-backfill.sh b/t/t5620-backfill.sh
index c2acd1339bd454..eecf03d5199ea9 100755
--- a/t/t5620-backfill.sh
+++ b/t/t5620-backfill.sh
@@ -77,6 +77,12 @@ test_expect_success 'do partial clone 2, backfill batch size' '
 	test_line_count = 0 revs2
 '
 
+test_expect_success 'backfill --sparse without sparse-checkout fails' '
+	git init not-sparse &&
+	test_must_fail git -C not-sparse backfill --sparse 2>err &&
+	grep "problem loading sparse-checkout" err
+'
+
 test_expect_success 'backfill --sparse' '
 	git clone --sparse --filter=blob:none		\
 		--single-branch --branch=main 		\
@@ -105,7 +111,12 @@ test_expect_success 'backfill --sparse' '
 	test_trace2_data promisor fetch_count 8 <sparse-trace2 &&
 	test_trace2_data path-walk paths 15 <sparse-trace2 &&
 	git -C backfill3 rev-list --quiet --objects --missing=print HEAD >missing &&
-	test_line_count = 24 missing
+	test_line_count = 24 missing &&
+
+	# Disabling the --sparse option (on by default) will download everything
+	git -C backfill3 backfill --no-sparse &&
+	git -C backfill3 rev-list --quiet --objects --missing=print HEAD >missing &&
+	test_line_count = 0 missing
 '
 
 test_expect_success 'backfill --sparse without cone mode' '