diff --git a/reactos/include/ndk/arm/mmtypes.h b/reactos/include/ndk/arm/mmtypes.h
index 255d89921f1..5c99bc24e4a 100644
--- a/reactos/include/ndk/arm/mmtypes.h
+++ b/reactos/include/ndk/arm/mmtypes.h
@@ -26,7 +26,9 @@ Author:
 //
 // Page-related Macros
 //
+#ifndef PAGE_SIZE
 #define PAGE_SIZE                         0x1000
+#endif
 #define PAGE_SHIFT                        12L
 #define MM_ALLOCATION_GRANULARITY         0x10000
 #define MM_ALLOCATION_GRANULARITY_SHIFT   16L
diff --git a/reactos/include/psdk/winnt.h b/reactos/include/psdk/winnt.h
index 9fe6023a334..ed3c4d35a96 100644
--- a/reactos/include/psdk/winnt.h
+++ b/reactos/include/psdk/winnt.h
@@ -2846,6 +2846,10 @@ typedef struct _CONTEXT {
 } CONTEXT;
 #elif defined(ARM)
 
+#ifndef PAGE_SIZE
+#define PAGE_SIZE                         0x1000 // FIXME: This should probably go elsewhere
+#endif
+    
 /* The following flags control the contents of the CONTEXT structure. */
 
 #define CONTEXT_ARM    0x0000040