diff --git a/roles/agent/defaults/main.yml b/roles/agent/defaults/main.yml
index a39a9e605..e82f3fbaf 100644
--- a/roles/agent/defaults/main.yml
+++ b/roles/agent/defaults/main.yml
@@ -4,6 +4,7 @@ checkmk_agent_edition: cre
 checkmk_agent_server_protocol: http
 checkmk_agent_server: localhost
 checkmk_agent_site: mysite
+checkmk_agent_registration_server_protocol: "{{ checkmk_agent_server_protocol }}"
 checkmk_agent_registration_server: "{{ checkmk_agent_server }}"
 checkmk_agent_registration_site: "{{ checkmk_agent_site }}"
 checkmk_agent_server_validate_certs: 'true'
diff --git a/roles/agent/molecule/2.1.0/group_vars/all.yml b/roles/agent/molecule/2.1.0/group_vars/all.yml
index 98bf3d455..0112736d4 100644
--- a/roles/agent/molecule/2.1.0/group_vars/all.yml
+++ b/roles/agent/molecule/2.1.0/group_vars/all.yml
@@ -12,6 +12,7 @@ checkmk_agent_edition: "{{ checkmk_var_edition }}"
 checkmk_agent_server_protocol: http
 checkmk_agent_server: 127.0.0.1
 checkmk_agent_site: "{{ checkmk_var_checkmk_site }}"
+checkmk_agent_registration_server_protocol: "{{ checkmk_agent_server_protocol }}"
 checkmk_agent_registration_server: "{{ checkmk_agent_server }}"
 checkmk_agent_registration_site: "{{ checkmk_agent_site }}"
 checkmk_agent_server_validate_certs: 'false'
diff --git a/roles/agent/molecule/2.2.0/group_vars/all.yml b/roles/agent/molecule/2.2.0/group_vars/all.yml
index 81d3f7f09..63daf8788 100644
--- a/roles/agent/molecule/2.2.0/group_vars/all.yml
+++ b/roles/agent/molecule/2.2.0/group_vars/all.yml
@@ -12,6 +12,7 @@ checkmk_agent_edition: "{{ checkmk_var_edition }}"
 checkmk_agent_server_protocol: http
 checkmk_agent_server: 127.0.0.1
 checkmk_agent_site: "{{ checkmk_var_checkmk_site }}"
+checkmk_agent_registration_server_protocol: "{{ checkmk_agent_server_protocol }}"
 checkmk_agent_registration_server: "{{ checkmk_agent_server }}"
 checkmk_agent_registration_site: "{{ checkmk_agent_site }}"
 checkmk_agent_server_validate_certs: 'false'
diff --git a/roles/agent/molecule/2.3.0/group_vars/all.yml b/roles/agent/molecule/2.3.0/group_vars/all.yml
index 77ff0e1ee..395449edd 100644
--- a/roles/agent/molecule/2.3.0/group_vars/all.yml
+++ b/roles/agent/molecule/2.3.0/group_vars/all.yml
@@ -12,6 +12,7 @@ checkmk_agent_edition: "{{ checkmk_var_edition }}"
 checkmk_agent_server_protocol: http
 checkmk_agent_server: 127.0.0.1
 checkmk_agent_site: "{{ checkmk_var_checkmk_site }}"
+checkmk_agent_registration_server_protocol: "{{ checkmk_agent_server_protocol }}"
 checkmk_agent_registration_server: "{{ checkmk_agent_server }}"
 checkmk_agent_registration_site: "{{ checkmk_agent_site }}"
 checkmk_agent_server_validate_certs: 'false'
diff --git a/roles/agent/tasks/Linux.yml b/roles/agent/tasks/Linux.yml
index 6ddc18fd9..f64ac6ca1 100644
--- a/roles/agent/tasks/Linux.yml
+++ b/roles/agent/tasks/Linux.yml
@@ -106,7 +106,7 @@
   become: true
   ansible.builtin.shell: |
     cmk-update-agent register -H {{ checkmk_agent_host_name }} \
-    -s {{ checkmk_agent_registration_server }} -i {{ checkmk_agent_registration_site }} -p {{ checkmk_agent_server_protocol }} \
+    -s {{ checkmk_agent_registration_server }} -i {{ checkmk_agent_registration_site }} -p {{ checkmk_agent_registration_server_protocol }} \
     -U {{ checkmk_agent_user }} -P {{ __checkmk_agent_auth }}
   no_log: "{{ checkmk_agent_no_log | bool }}"
   register: __checkmk_agent_update_state
@@ -122,7 +122,7 @@
   become: true
   ansible.builtin.shell: |
     cmk-update-agent register -H {{ checkmk_agent_host_name }} \
-    -s {{ checkmk_agent_registration_server }} -i {{ checkmk_agent_registration_site }} -p {{ checkmk_agent_server_protocol }} \
+    -s {{ checkmk_agent_registration_server }} -i {{ checkmk_agent_registration_site }} -p {{ checkmk_agent_registration_server_protocol }} \
     -U {{ checkmk_agent_user }} -S {{ __checkmk_agent_auth }}
   no_log: "{{ checkmk_agent_no_log | bool }}"
   register: __checkmk_agent_update_state
diff --git a/roles/agent/tasks/Win32NT.yml b/roles/agent/tasks/Win32NT.yml
index 5cbe3eb95..189fa8766 100644
--- a/roles/agent/tasks/Win32NT.yml
+++ b/roles/agent/tasks/Win32NT.yml
@@ -74,7 +74,7 @@
 - name: "{{ ansible_system }}: Register Agent for automatic Updates using Automation Secret."  # noqa no-changed-when
   ansible.windows.win_command: |
     check_mk_agent.exe updater register -H {{ checkmk_agent_host_name }} \
-    -s {{ checkmk_agent_registration_server }} -i {{ checkmk_agent_registration_site }} -p {{ checkmk_agent_server_protocol }} \
+    -s {{ checkmk_agent_registration_server }} -i {{ checkmk_agent_registration_site }} -p {{ checkmk_agent_registration_server_protocol }} \
     -U {{ checkmk_agent_user }} -S {{ __checkmk_agent_auth }}
   no_log: "{{ checkmk_agent_no_log | bool }}"
   register: __checkmk_agent_update_state