diff --git a/build.py b/build.py
index 611a275..b860e5c 100755
--- a/build.py
+++ b/build.py
@@ -70,6 +70,7 @@ else: # 'debug'
     cc_flags.append('-g')
     cc_flags.append('-O0')
     cc_defines.append('DEBUG')
+cc_defines.append(f'_CIA_OS_{target.upper()}')
 
 # Generate TinyRT headers for the target platform
 print(f"==> Generating TinyRT header for {target}")
diff --git a/include/cia-def.h b/include/cia-def.h
index 89551bf..a4d2be9 100644
--- a/include/cia-def.h
+++ b/include/cia-def.h
@@ -6,40 +6,14 @@
 #define noreturn _Noreturn
 #define NULL ((void *)0)
 
-// Platform macros
-#define _CIA_LINUX   1
-#define _CIA_WINDOWS 2
-#define _CIA_ANDROID 3
-
-// Platform detection
-#if defined(WIN32) || defined(_WIN32) || defined(__WIN32__) || defined(__NT__)
-   #define _CIA_OS _CIA_WINDOWS
-   #if !defined(_WIN64)
-      #error "32-bit windows is not supported"
-   #endif
-#elif __APPLE__
-    #error "Apple OS's not supported and will never be unless you want to write the support for it"
-#elif __ANDROID__
-    #define _CIA_OS _CIA_ANDROID
-#elif __linux__
-    #define _CIA_OS _CIA_LINUX
-#else
-    #error "Unable to detect the OS"
-#endif
-
-// Convenience platform checking macros
-#define _CIA_OS_LINUX()   (_CIA_OS == _CIA_LINUX)
-#define _CIA_OS_WINDOWS() (_CIA_OS == _CIA_WINDOWS)
-#define _CIA_OS_ANDROID() (_CIA_OS == _CIA_ANDROID)
-
 // Assert commonly-accepted platform-invariant sizes
 static_assert(sizeof(char) == 1, "Char isn't 1 bytes long");
 static_assert(sizeof(short) == 2, "Short isn't 2 bytes long");
 static_assert(sizeof(int) == 4, "Int isn't 4 bytes long");
 static_assert(sizeof(long long int) == 8, "Long long isn't 8 bytes long");
-#if _CIA_OS_LINUX()
+#if defined(_CIA_OS_LINUX)
     static_assert(sizeof(long) == 8, "Long on linux isn't 8 bytes");
-#elif _CIA_OS_WINDOWS()
+#elif defined(_CIA_OS_WINDOWS)
     static_assert(sizeof(long) == 4, "Long on windows isn't 4 bytes");
 #endif
 
@@ -50,10 +24,10 @@ typedef signed short int16_t;
 typedef unsigned short uint16_t;
 typedef signed int int32_t;
 typedef unsigned int uint32_t;
-#if _CIA_OS_LINUX()
+#if defined(_CIA_OS_LINUX)
     typedef signed long int64_t;
     typedef unsigned long uint64_t;
-#elif _CIA_OS_WINDOWS()
+#elif defined(_CIA_OS_WINDOWS)
     typedef signed long long int64_t;
     typedef unsigned long long uint64_t;
 #else