diff --git a/pyanaconda/modules/payloads/payload/rpm_ostree/installation.py b/pyanaconda/modules/payloads/payload/rpm_ostree/installation.py
index eb0245960b5..75d3673ccc4 100644
--- a/pyanaconda/modules/payloads/payload/rpm_ostree/installation.py
+++ b/pyanaconda/modules/payloads/payload/rpm_ostree/installation.py
@@ -569,7 +569,7 @@ def _set_kargs(self):
             device_tree.GetDeviceData(root_name)
         )
 
-        set_kargs_args = ["admin", "instutil", "set-kargs"]
+        set_kargs_args = ["admin", "instutil", "set-kargs", "--merge"]
         set_kargs_args.extend(bootloader.GetArguments())
         set_kargs_args.append("root=" + device_tree.GetFstabSpec(root_name))
 
diff --git a/tests/unit_tests/pyanaconda_tests/modules/payloads/payload/test_rpm_ostree_tasks.py b/tests/unit_tests/pyanaconda_tests/modules/payloads/payload/test_rpm_ostree_tasks.py
index 940685b73cf..05632fcf441 100644
--- a/tests/unit_tests/pyanaconda_tests/modules/payloads/payload/test_rpm_ostree_tasks.py
+++ b/tests/unit_tests/pyanaconda_tests/modules/payloads/payload/test_rpm_ostree_tasks.py
@@ -706,8 +706,15 @@ def test_btrfs_run(self, devdata_mock, storage_mock, symlink_mock, rename_mock,
             )
             exec_mock.assert_called_once_with(
                 "ostree",
-                ["admin", "instutil", "set-kargs", "BOOTLOADER-ARGS", "root=FSTAB-SPEC",
-                 "rootflags=subvol=device-name", "rw"],
+                ["admin",
+                 "instutil",
+                 "set-kargs",
+                 "--merge",
+                 "BOOTLOADER-ARGS",
+                 "root=FSTAB-SPEC",
+                 "rootflags=subvol=device-name",
+                 "rw"
+                 ],
                 root=sysroot
             )
 
@@ -743,7 +750,14 @@ def test_nonbtrfs_run(self, devdata_mock, storage_mock, symlink_mock, rename_moc
             )
             exec_mock.assert_called_once_with(
                 "ostree",
-                ["admin", "instutil", "set-kargs", "BOOTLOADER-ARGS", "root=FSTAB-SPEC", "rw"],
+                ["admin",
+                 "instutil",
+                 "set-kargs",
+                 "--merge",
+                 "BOOTLOADER-ARGS",
+                 "root=FSTAB-SPEC",
+                 "rw"
+                 ],
                 root=sysroot
             )
 
@@ -784,7 +798,14 @@ def test_bootupd_run(self, devdata_mock, storage_mock, symlink_mock, rename_mock
                 ),
                 call(
                     "ostree",
-                    ["admin", "instutil", "set-kargs", "BOOTLOADER-ARGS", "root=FSTAB-SPEC", "rw"],
+                    ["admin",
+                     "instutil",
+                     "set-kargs",
+                     "--merge",
+                     "BOOTLOADER-ARGS",
+                     "root=FSTAB-SPEC",
+                     "rw"
+                     ],
                     root=sysroot
                 )
             ])
@@ -826,7 +847,14 @@ def test_bootupd_run_with_leavebootorder(self, devdata_mock, storage_mock, symli
                 ),
                 call(
                     "ostree",
-                    ["admin", "instutil", "set-kargs", "BOOTLOADER-ARGS", "root=FSTAB-SPEC", "rw"],
+                    ["admin",
+                     "instutil",
+                     "set-kargs",
+                     "--merge",
+                     "BOOTLOADER-ARGS",
+                     "root=FSTAB-SPEC",
+                     "rw"
+                     ],
                     root=sysroot
                 )
             ])