diff --git a/src/nostalgia/core/config.hpp b/src/nostalgia/core/config.hpp
index 5fdc4fb8..5387b3f1 100644
--- a/src/nostalgia/core/config.hpp
+++ b/src/nostalgia/core/config.hpp
@@ -9,9 +9,7 @@
 
 #include <ox/std/types.hpp>
 
-namespace nostalgia::core {
-
-namespace config {
+namespace nostalgia::core::config {
 
 constexpr auto ImGuiEnabled =
 #if __has_include(<imgui.h>)
@@ -28,11 +26,8 @@ enum class SdlVsync {
 
 constexpr auto GbaSpriteBufferLen = 128;
 constexpr auto GbaEventLoopTimerBased = false;
+constexpr auto GbaTimerBits = 32;
 constexpr auto UserlandFpsPrint = false;
 constexpr auto SdlVsyncOption = static_cast<int>(SdlVsync::Adaptive);
 
 }
-
-using gba_timer_t = uint32_t;
-
-}
diff --git a/src/nostalgia/core/gba/core.arm.cpp b/src/nostalgia/core/gba/core.arm.cpp
index ca646cd7..3055b2dc 100644
--- a/src/nostalgia/core/gba/core.arm.cpp
+++ b/src/nostalgia/core/gba/core.arm.cpp
@@ -8,6 +8,7 @@
 #include "addresses.hpp"
 #include "bios.hpp"
 #include "irq.hpp"
+#include "core.hpp"
 
 extern "C" void isr();
 
diff --git a/src/nostalgia/core/gba/core.cpp b/src/nostalgia/core/gba/core.cpp
index 613d5cbd..8ad054f5 100644
--- a/src/nostalgia/core/gba/core.cpp
+++ b/src/nostalgia/core/gba/core.cpp
@@ -9,6 +9,7 @@
 #include "addresses.hpp"
 #include "bios.hpp"
 #include "irq.hpp"
+#include "core.hpp"
 
 extern "C" void isr();
 
diff --git a/src/nostalgia/core/gba/core.hpp b/src/nostalgia/core/gba/core.hpp
new file mode 100644
index 00000000..0b27def7
--- /dev/null
+++ b/src/nostalgia/core/gba/core.hpp
@@ -0,0 +1,15 @@
+/*
+ * Copyright 2016 - 2022 Gary Talent (gary@drinkingtea.net). All rights reserved.
+ */
+
+#pragma once
+
+#include <ox/std/types.hpp>
+
+#include <nostalgia/core/config.hpp>
+
+namespace nostalgia::core {
+
+using gba_timer_t = ox::Uint<config::GbaTimerBits>;
+
+}
\ No newline at end of file
diff --git a/src/nostalgia/core/gba/irq.arm.cpp b/src/nostalgia/core/gba/irq.arm.cpp
index 32b07a7e..27485c75 100644
--- a/src/nostalgia/core/gba/irq.arm.cpp
+++ b/src/nostalgia/core/gba/irq.arm.cpp
@@ -8,6 +8,7 @@
 #include <ox/std/bit.hpp>
 
 #include "addresses.hpp"
+#include "core.hpp"
 #include "gfx.hpp"
 #include "irq.hpp"