diff --git a/CMakeLists.txt b/CMakeLists.txt
index 884bcdb..f4efc60 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,5 +1,7 @@
-cmake_minimum_required(VERSION 3.10)
+cmake_minimum_required(VERSION 3.12)
 project(fcitx5-libthai VERSION 5.1.4)
+
+set(REQUIRED_FCITX_VERSION 5.1.12)
 find_package(ECM REQUIRED 1.0.0)
 set(CMAKE_MODULE_PATH ${ECM_MODULE_PATH} "${CMAKE_CURRENT_SOURCE_DIR}/cmake" ${CMAKE_MODULE_PATH})
 include(FeatureSummary)
@@ -7,7 +9,7 @@ include(GNUInstallDirs)
 include(ECMUninstallTarget)
 
 find_package(PkgConfig REQUIRED)
-find_package(Fcitx5Core 5.0.2 REQUIRED)
+find_package(Fcitx5Core ${REQUIRED_FCITX_VERSION} REQUIRED)
 find_package(Iconv REQUIRED)
 find_package(Gettext REQUIRED)
 
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index f3d4ed0..be9f031 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -1,5 +1,5 @@
 
-add_library(iconvwrapper STATIC iconvwrapper.cpp)
+add_library(iconvwrapper OBJECT iconvwrapper.cpp)
 set_target_properties(iconvwrapper PROPERTIES POSITION_INDEPENDENT_CODE ON)
 target_link_libraries(iconvwrapper Fcitx5::Utils Iconv::Iconv)
 
@@ -7,7 +7,7 @@ set(LIBTHAI_SOURCES
     engine.cpp
     thaikb.cpp
 )
-add_library(libthai MODULE ${LIBTHAI_SOURCES})
+add_fcitx5_addon(libthai ${LIBTHAI_SOURCES})
 target_link_libraries(libthai iconvwrapper Fcitx5::Core ${THAI_TARGET} Iconv::Iconv)
 target_include_directories(libthai PRIVATE ${PROJECT_BINARY_DIR})
 set_target_properties(libthai PROPERTIES PREFIX "")
diff --git a/src/engine.cpp b/src/engine.cpp
index 1c5ad52..87447f3 100644
--- a/src/engine.cpp
+++ b/src/engine.cpp
@@ -5,18 +5,38 @@
  *
  */
 #include "engine.h"
+#include "thaikb.h"
+#include <cstddef>
+#include <cstdint>
+#include <cstring>
 #include <deque>
+#include <fcitx-utils/capabilityflags.h>
+#include <fcitx-utils/key.h>
+#include <fcitx-utils/keysym.h>
+#include <fcitx-utils/keysymgen.h>
 #include <fcitx-utils/log.h>
 #include <fcitx-utils/utf8.h>
+#include <fcitx/addoninstance.h>
+#include <fcitx/event.h>
 #include <fcitx/inputcontext.h>
 #include <fcitx/inputcontextmanager.h>
+#include <fcitx/inputmethodentry.h>
+#include <stdexcept>
+#include <string>
+#include <string_view>
+#include <thai/thailib.h>
 #include <thai/thcell.h>
 #include <thai/thinp.h>
+#include <vector>
 
-namespace fcitx {
+namespace {
 
 FCITX_DEFINE_LOG_CATEGORY(libthai_log, "libthai");
 
+}
+
+namespace fcitx {
+
 #define LIBTHAI_DEBUG() FCITX_LOGC(libthai_log, Debug)
 
 constexpr auto FALLBACK_BUFF_SIZE = 4;
@@ -99,11 +119,13 @@ LibThaiEngine::LibThaiEngine(Instance *instance)
 
 LibThaiEngine::~LibThaiEngine() {}
 
-void LibThaiEngine::activate(const InputMethodEntry &, InputContextEvent &) {}
+void LibThaiEngine::activate(const InputMethodEntry & /*entry*/,
+                             InputContextEvent & /*event*/) {}
 
-void LibThaiEngine::deactivate(const InputMethodEntry &, InputContextEvent &) {}
+void LibThaiEngine::deactivate(const InputMethodEntry & /*entry*/,
+                               InputContextEvent & /*event*/) {}
 
-bool isContextIntactKey(Key key) {
+static bool isContextIntactKey(Key key) {
 
     return (((key.sym() & 0xFF00) == 0xFF00) &&
             (/* IsModifierKey */
@@ -114,7 +136,7 @@ bool isContextIntactKey(Key key) {
              key.sym() <= FcitxKey_ISO_Last_Group_Lock));
 }
 
-bool isContextLostKey(Key key) {
+static bool isContextLostKey(Key key) {
 
     return ((key.sym() & 0xFF00) == 0xFF00) &&
            (key.sym() == FcitxKey_BackSpace || key.sym() == FcitxKey_Tab ||
@@ -134,12 +156,13 @@ bool isContextLostKey(Key key) {
             (FcitxKey_F1 <= key.sym() && key.sym() <= FcitxKey_F35));
 }
 
-void LibThaiEngine::keyEvent(const InputMethodEntry &, KeyEvent &keyEvent) {
+void LibThaiEngine::keyEvent(const InputMethodEntry & /*entry*/,
+                             KeyEvent &keyEvent) {
     auto key = keyEvent.rawKey();
     if (keyEvent.isRelease()) {
         return;
     }
-    auto state = keyEvent.inputContext()->propertyFor(&factory_);
+    auto *state = keyEvent.inputContext()->propertyFor(&factory_);
     // If any ctrl alt super modifier is pressed, ignore.
     if (key.states().testAny(KeyStates{KeyState::Ctrl_Alt, KeyState::Super}) ||
         isContextLostKey(key)) {
@@ -187,7 +210,7 @@ void LibThaiEngine::keyEvent(const InputMethodEntry &, KeyEvent &keyEvent) {
             prevChar = prevChars.back();
         }
         if (!th_isaccept(prevChar, newChar, *config_.strictness)) {
-            return keyEvent.filterAndAccept();
+             keyEvent.filterAndAccept(); return;
         }
         if (state->commitString(&newChar, 1)) {
             keyEvent.filterAndAccept();
@@ -200,14 +223,14 @@ void LibThaiEngine::keyEvent(const InputMethodEntry &, KeyEvent &keyEvent) {
     state->prevCell(&contextCell);
     if (!th_validate_leveled(contextCell, newChar, &conv,
                              *config_.strictness)) {
-        return keyEvent.filterAndAccept();
+         keyEvent.filterAndAccept(); return;
     }
 
     if (conv.offset < 0) {
         // SurroundingText not supported, so just reject the key.
         if (!keyEvent.inputContext()->capabilityFlags().test(
                 CapabilityFlag::SurroundingText)) {
-            return keyEvent.filter();
+             keyEvent.filter(); return;
         }
 
         keyEvent.inputContext()->deleteSurroundingText(conv.offset,
@@ -217,15 +240,15 @@ void LibThaiEngine::keyEvent(const InputMethodEntry &, KeyEvent &keyEvent) {
     state->rememberPrevChars(newChar);
     if (state->commitString(conv.conv,
                             strlen(reinterpret_cast<char *>(conv.conv)))) {
-        return keyEvent.filterAndAccept();
+         keyEvent.filterAndAccept(); return;
     }
 }
 
-void LibThaiEngine::reset(const InputMethodEntry &, InputContextEvent &event) {
-    auto state = event.inputContext()->propertyFor(&factory_);
+void LibThaiEngine::reset(const InputMethodEntry & /*entry*/, InputContextEvent &event) {
+    auto *state = event.inputContext()->propertyFor(&factory_);
     state->forgetPrevChars();
 }
 
 } // namespace fcitx
 
-FCITX_ADDON_FACTORY(fcitx::LibThaiFactory);
+FCITX_ADDON_FACTORY_V2(libthai, fcitx::LibThaiFactory);
diff --git a/src/engine.h b/src/engine.h
index c62f58d..653ae5d 100644
--- a/src/engine.h
+++ b/src/engine.h
@@ -9,10 +9,16 @@
 
 #include "iconvwrapper.h"
 #include "thaikb.h"
+#include <fcitx-config/configuration.h>
+#include <fcitx-config/enum.h>
 #include <fcitx-config/iniparser.h>
+#include <fcitx-config/option.h>
+#include <fcitx-config/rawconfig.h>
 #include <fcitx-utils/i18n.h>
 #include <fcitx/addonfactory.h>
+#include <fcitx/addoninstance.h>
 #include <fcitx/addonmanager.h>
+#include <fcitx/event.h>
 #include <fcitx/inputcontextproperty.h>
 #include <fcitx/inputmethodengine.h>
 #include <fcitx/instance.h>
@@ -47,7 +53,7 @@ class LibThaiEngine final : public InputMethodEngine {
     void keyEvent(const InputMethodEntry &entry, KeyEvent &keyEvent) override;
     void reset(const InputMethodEntry &entry,
                InputContextEvent &event) override;
-    void deactivate(const fcitx::InputMethodEntry &,
+    void deactivate(const fcitx::InputMethodEntry & /*entry*/,
                     fcitx::InputContextEvent &event) override;
     const fcitx::Configuration *getConfig() const override { return &config_; }
     void setConfig(const fcitx::RawConfig &raw) override {
diff --git a/src/iconvwrapper.cpp b/src/iconvwrapper.cpp
index 972b8ce..cb93d40 100644
--- a/src/iconvwrapper.cpp
+++ b/src/iconvwrapper.cpp
@@ -6,8 +6,14 @@
  */
 
 #include "iconvwrapper.h"
+#include <cstddef>
+#include <cstdint>
 #include <fcitx-utils/utf8.h>
 #include <iconv.h>
+#include <iterator>
+#include <memory>
+#include <string_view>
+#include <vector>
 
 class IconvWrapperPrivate {
 public:
@@ -30,7 +36,7 @@ IconvWrapper::operator bool() const {
 }
 
 std::vector<uint8_t> IconvWrapper::tryConvert(std::string_view s) const {
-    auto conv = d_ptr->conv_;
+    iconv_t conv = d_ptr->conv_;
     for (auto iter = std::begin(s), e = std::end(s); iter != e;
          iter = fcitx::utf8::nextChar(iter)) {
         std::vector<uint8_t> result;
diff --git a/src/libthai-addon.conf.in.in b/src/libthai-addon.conf.in.in
index c1c223a..6cff9fe 100644
--- a/src/libthai-addon.conf.in.in
+++ b/src/libthai-addon.conf.in.in
@@ -6,3 +6,6 @@ Library=libthai
 Type=SharedLibrary
 OnDemand=True
 Configurable=True
+
+[Addon/Dependencies]
+0=core:@REQUIRED_FCITX_VERSION@