diff --git a/include/def.h b/include/def.h
index 2dc1cb7..e8fae87 100644
--- a/include/def.h
+++ b/include/def.h
@@ -9,6 +9,24 @@
 
 namespace ipc {
 
+// pre-defined
+
+#ifdef IPC_UNUSED_
+#   error "IPC_UNUSED_ has been defined."
+#endif
+
+#if __cplusplus >= 201703L
+#   define IPC_UNUSED_ [[maybe_unused]]
+#else /*__cplusplus < 201703L*/
+#if defined(_MSC_VER)
+#   define IPC_UNUSED_ __pragma(warning(suppress: 4100 4101 4189))
+#elif defined(__GNUC__)
+#   define IPC_UNUSED_ __attribute__((__unused__))
+#else
+#   define IPC_UNUSED_
+#endif
+#endif/*__cplusplus < 201703L*/
+
 // types
 
 using byte_t = std::uint8_t;
diff --git a/src/memory/resource.hpp b/src/memory/resource.hpp
index c3a6daf..6573643 100644
--- a/src/memory/resource.hpp
+++ b/src/memory/resource.hpp
@@ -7,6 +7,8 @@
 #include <unordered_map>
 #include <vector>
 
+#include "def.h"
+
 #include "memory/alloc.hpp"
 #include "memory/wrapper.hpp"
 
@@ -32,7 +34,7 @@ constexpr void static_for(std::index_sequence<I...>, F&& f) {
 #else /*__cplusplus < 201703L*/
 inline void static_for(std::index_sequence<I...>, F&& f) {
 #endif/*__cplusplus < 201703L*/
-    [[maybe_unused]] auto expand = { (f(std::integral_constant<size_t, I>{}), 0)... };
+    auto IPC_UNUSED_ expand = { (f(std::integral_constant<size_t, I>{}), 0)... };
 }
 
 template <std::size_t Size>
diff --git a/src/memory/wrapper.hpp b/src/memory/wrapper.hpp
index b96d15d..92f7416 100644
--- a/src/memory/wrapper.hpp
+++ b/src/memory/wrapper.hpp
@@ -12,6 +12,7 @@
 #include <cstddef>
 #include <type_traits>
 
+#include "def.h"
 #include "rw_lock.h"
 #include "tls_pointer.h"
 
@@ -52,7 +53,7 @@ private:
         alloc_t(synchronized* t)
             : t_ { t } {
             {
-                [[maybe_unused]] auto guard = ipc::detail::unique_lock(t_->lc_);
+                auto IPC_UNUSED_ guard = ipc::detail::unique_lock(t_->lc_);
                 auto it = t_->allocs_.begin();
                 if (it != t_->allocs_.end()) {
                     std::tie(s_, a_) = *it;
@@ -65,7 +66,7 @@ private:
         }
 
         ~alloc_t() {
-            [[maybe_unused]] auto guard = ipc::detail::unique_lock(t_->lc_);
+            auto IPC_UNUSED_ guard = ipc::detail::unique_lock(t_->lc_);
             t_->allocs_.emplace(s_, a_);
         }
 
diff --git a/src/platform/shm_linux.cpp b/src/platform/shm_linux.cpp
index a8f50f2..baf79e0 100644
--- a/src/platform/shm_linux.cpp
+++ b/src/platform/shm_linux.cpp
@@ -11,6 +11,7 @@
 #include <utility>
 #include <mutex>
 
+#include "def.h"
 #include "memory/resource.hpp"
 
 namespace {
@@ -65,7 +66,7 @@ void* acquire(char const * name, std::size_t size) {
     auto acc = acc_of(mem);
     acc->fetch_add(1, std::memory_order_release);
     {
-        [[maybe_unused]] auto guard = ipc::detail::unique_lock(m2h()->lc_);
+        auto IPC_UNUSED_ guard = ipc::detail::unique_lock(m2h()->lc_);
         m2h()->cache_.emplace(++acc, std::move(op_name));
     }
     return acc;
@@ -75,7 +76,7 @@ void release(void* mem, std::size_t size) {
     if (mem == nullptr) {
         return;
     }
-    [[maybe_unused]] auto guard = ipc::detail::unique_lock(m2h()->lc_);
+    auto IPC_UNUSED_ guard = ipc::detail::unique_lock(m2h()->lc_);
     auto& cc = m2h()->cache_;
     auto it = cc.find(mem);
     if (it == cc.end()) {
diff --git a/src/platform/shm_win.cpp b/src/platform/shm_win.cpp
index 6136414..225e38b 100644
--- a/src/platform/shm_win.cpp
+++ b/src/platform/shm_win.cpp
@@ -43,7 +43,7 @@ void* acquire(char const * name, std::size_t size) {
         return nullptr;
     }
     {
-        [[maybe_unused]] auto guard = ipc::detail::unique_lock(m2h()->lc_);
+        auto IPC_UNUSED_ guard = ipc::detail::unique_lock(m2h()->lc_);
         m2h()->cache_.emplace(mem, h);
     }
     return mem;
@@ -53,7 +53,7 @@ void release(void* mem, std::size_t /*size*/) {
     if (mem == nullptr) {
         return;
     }
-    [[maybe_unused]] auto guard = ipc::detail::unique_lock(m2h()->lc_);
+    auto IPC_UNUSED_ guard = ipc::detail::unique_lock(m2h()->lc_);
     auto& cc = m2h()->cache_;
     auto it = cc.find(mem);
     if (it == cc.end()) {
diff --git a/src/platform/waiter_linux.h b/src/platform/waiter_linux.h
index a0f704f..2ffec49 100644
--- a/src/platform/waiter_linux.h
+++ b/src/platform/waiter_linux.h
@@ -7,6 +7,8 @@
 #include <memory>
 #include <type_traits>
 
+#include "def.h"
+
 #if __cplusplus >= 201703L
 namespace std {
 
@@ -58,7 +60,7 @@ public:
             if (::pthread_mutexattr_init(&mutex_attr) != 0) {
                 return invalid();
             }
-            [[maybe_unused]] auto guard_mutex_attr = unique_ptr(&mutex_attr, ::pthread_mutexattr_destroy);
+            auto IPC_UNUSED_ guard_mutex_attr = unique_ptr(&mutex_attr, ::pthread_mutexattr_destroy);
             if (::pthread_mutexattr_setpshared(&mutex_attr, PTHREAD_PROCESS_SHARED) != 0) {
                 return invalid();
             }
@@ -71,7 +73,7 @@ public:
             if (::pthread_condattr_init(&cond_attr) != 0) {
                 return invalid();
             }
-            [[maybe_unused]] auto guard_cond_attr = unique_ptr(&cond_attr, ::pthread_condattr_destroy);
+            auto IPC_UNUSED_ guard_cond_attr = unique_ptr(&cond_attr, ::pthread_condattr_destroy);
             if (::pthread_condattr_setpshared(&cond_attr, PTHREAD_PROCESS_SHARED) != 0) {
                 return invalid();
             }
@@ -100,7 +102,7 @@ public:
         if (::pthread_mutex_lock(&(w->mutex_)) != 0) {
             return false;
         }
-        [[maybe_unused]] auto guard = unique_ptr(&(w->mutex_), ::pthread_mutex_unlock);
+        auto IPC_UNUSED_ guard = unique_ptr(&(w->mutex_), ::pthread_mutex_unlock);
         if (::pthread_cond_wait(&(w->cond_), &(w->mutex_)) != 0) {
             return false;
         }