diff --git a/core/commands/object/patch.go b/core/commands/object/patch.go
index c98f12506..78f927032 100644
--- a/core/commands/object/patch.go
+++ b/core/commands/object/patch.go
@@ -4,13 +4,20 @@ import (
 	"fmt"
 	"io"
 
+	"github.com/ipfs/go-cid"
 	cmds "github.com/ipfs/go-ipfs-cmds"
 	"github.com/ipfs/go-ipfs/core/commands/cmdenv"
+	coreiface "github.com/ipfs/interface-go-ipfs-core"
 
 	"github.com/ipfs/interface-go-ipfs-core/options"
 	"github.com/ipfs/interface-go-ipfs-core/path"
 )
 
+const (
+	softBlockLimit = 1024 * 1024 // https://github.com/ipfs/go-ipfs/issues/7421#issuecomment-910833499
+	allowBigBlock  = "allow-big-block"
+)
+
 var ObjectPatchCmd = &cmds.Command{
 	Helptext: cmds.HelpText{
 		Tagline: "Deprecated way to create a new merkledag object based on an existing one. Use MFS with 'files cp|rm' instead.",
@@ -41,6 +48,9 @@ For modern use cases, use MFS with 'files' commands: 'ipfs files --help'.
 		"rm-link":     patchRmLinkCmd,
 		"set-data":    patchSetDataCmd,
 	},
+	Options: []cmds.Option{
+		cmds.BoolOption(allowBigBlock, "Disable block size check and allow creation of blocks bigger than 1MB. WARNING: such blocks won't be transferable over the standard bitswap.").WithDefault(false),
+	},
 }
 
 var patchAppendDataCmd = &cmds.Command{
@@ -82,6 +92,10 @@ DEPRECATED and provided for legacy reasons. Use 'ipfs add' or 'ipfs files' inste
 			return err
 		}
 
+		if err := checkBlockSize(req, p.Cid(), api.Dag()); err != nil {
+			return err
+		}
+
 		return cmds.EmitOnce(res, &Object{Hash: p.Cid().String()})
 	},
 	Type: &Object{},
@@ -128,6 +142,10 @@ DEPRECATED and provided for legacy reasons. Use 'files cp' and 'dag put' instead
 			return err
 		}
 
+		if err := checkBlockSize(req, p.Cid(), api.Dag()); err != nil {
+			return err
+		}
+
 		return cmds.EmitOnce(res, &Object{Hash: p.Cid().String()})
 	},
 	Type: Object{},
@@ -166,6 +184,10 @@ DEPRECATED and provided for legacy reasons. Use 'files rm' instead.
 			return err
 		}
 
+		if err := checkBlockSize(req, p.Cid(), api.Dag()); err != nil {
+			return err
+		}
+
 		return cmds.EmitOnce(res, &Object{Hash: p.Cid().String()})
 	},
 	Type: Object{},
@@ -232,6 +254,10 @@ Use MFS and 'files' commands instead:
 			return err
 		}
 
+		if err := checkBlockSize(req, p.Cid(), api.Dag()); err != nil {
+			return err
+		}
+
 		return cmds.EmitOnce(res, &Object{Hash: p.Cid().String()})
 	},
 	Type: Object{},
@@ -242,3 +268,26 @@ Use MFS and 'files' commands instead:
 		}),
 	},
 }
+
+func checkBlockSize(req *cmds.Request, c cid.Cid, dagAPI coreiface.APIDagService) error {
+	allowAnyBlockSize, _ := req.Options[allowBigBlock].(bool)
+	if allowAnyBlockSize {
+		return nil
+	}
+
+	// We do not allow producing blocks bigger than 1 MiB to avoid errors
+	// when transmitting them over BitSwap. The 1 MiB constant is an
+	// unenforced and undeclared rule of thumb hard-coded here.
+	modifiedNode, err := dagAPI.Get(req.Context, c)
+	if err != nil {
+		return err
+	}
+	modifiedNodeSize, err := modifiedNode.Size()
+	if err != nil {
+		return err
+	}
+	if modifiedNodeSize > softBlockLimit {
+		return fmt.Errorf("produced block is over 1MB, object API is deprecated and does not support HAMT-sharding: to create big directories, please use the files API (MFS)")
+	}
+	return nil
+}
diff --git a/test/sharness/t0051-object.sh b/test/sharness/t0051-object.sh
index 95de4fda7..875548411 100755
--- a/test/sharness/t0051-object.sh
+++ b/test/sharness/t0051-object.sh
@@ -223,6 +223,24 @@ test_object_cmd() {
     ipfs object stat $OUTPUT
   '
 
+  test_expect_success "'ipfs object patch' check output block size" '
+    DIR=$(ipfs object new unixfs-dir)
+    for i in {1..13}
+    do
+       DIR=$(ipfs object patch "$DIR" add-link "$DIR.jpg" "$DIR")
+    done
+    # Fail when new block goes over the BS limit of 1MB, but allow manual override
+    test_expect_code 1 ipfs object patch "$DIR" add-link "$DIR.jpg" "$DIR"  >patch_out 2>&1
+  '
+
+  test_expect_success "ipfs object patch add-link output has the correct error" '
+    grep "produced block is over 1MB, object API is deprecated and does not support HAMT-sharding: to create big directories, please use the files API (MFS)" patch_out
+  '
+
+  test_expect_success "ipfs object patch --allow-big-block=true add-link works" '
+    test_expect_code 0 ipfs object patch --allow-big-block=true "$DIR" add-link "$DIR.jpg" "$DIR"
+  '
+
   test_expect_success "'ipfs object new foo' shouldn't crash" '
     test_expect_code 1 ipfs object new foo
   '