diff --git a/gfx.h b/gfx.h
index 48a92770..9afb3256 100644
--- a/gfx.h
+++ b/gfx.h
@@ -35,7 +35,12 @@
  * @brief   Generic 'true' boolean constant.
  */
 #if !defined(TRUE) || defined(__DOXYGEN__)
-	#define TRUE        -1
+ 	// Keil/ARMCC requires some special threatment. can probably be generalized to always be 1.
+ 	#if (GFX_COMPILER == GFX_COMPILER_ARMCC) || (GFX_COMPILER == GFX_COMPILER_KEIL)
+		#define TRUE		1
+	#else
+		#define TRUE        -1
+ 	#endif
 #endif
 
 /**
@@ -57,7 +62,7 @@
 #if GFX_NO_INLINE
 	#define GFXINLINE
 #else
-	#if defined(__KEIL__) || defined(__C51__)
+	#if (GFX_COMPILER == GFX_COMPILER_ARMCC) || (GFX_COMPILER == GFX_COMPILER_KEIL)
 		#define GFXINLINE	__inline
 	#else
 		#define GFXINLINE	inline
diff --git a/src/gos/gos_x_threads.c b/src/gos/gos_x_threads.c
index 8a781b21..ea6e1852 100644
--- a/src/gos/gos_x_threads.c
+++ b/src/gos/gos_x_threads.c
@@ -203,12 +203,12 @@ static thread		mainthread;				// The main thread context
 	 * If they don't exist compile them to be the standard setjmp() function.
 	 * Similarly for longjmp().
 	 */
-	#if (!defined(setjmp) && !defined(_setjmp)) || defined(__KEIL__) || defined(__C51__)
+	#if (!defined(setjmp) && !defined(_setjmp)) || (GFX_COMPILER == GFX_COMPILER_ARMCC) || (GFX_COMPILER == GFX_COMPILER_KEIL)
 		#define CXT_SAVE 		setjmp
 	#else
 		#define CXT_SAVE 		_setjmp
 	#endif
-	#if (!defined(longjmp) && !defined(_longjmp)) || defined(__KEIL__) || defined(__C51__)
+	#if (!defined(longjmp) && !defined(_longjmp)) || (GFX_COMPILER == GFX_COMPILER_ARMCC) || (GFX_COMPILER == GFX_COMPILER_KEIL)
 		#define CXT_RESTORE 	longjmp
 	#else
 		#define CXT_RESTORE 	_longjmp
diff --git a/src/gwin/gwin_class.h b/src/gwin/gwin_class.h
index 7946a839..6a3f62b4 100644
--- a/src/gwin/gwin_class.h
+++ b/src/gwin/gwin_class.h
@@ -23,7 +23,7 @@
 
 #if GFX_USE_GWIN || defined(__DOXYGEN__)
 
-#if defined(__KEIL__) || defined(__C51__)
+#if (GFX_COMPILER == GFX_COMPILER_ARMCC) || (GFX_COMPILER == GFX_COMPILER_KEIL)
 	#pragma anon_unions
 #endif