diff --git a/src/harfbuzz-impl.h b/src/harfbuzz-impl.h
index 2531014153a089b10868212d7ead5fece6e5e0da..78fb1eccd5ecbd8df9e3196e1bbe6770b150fc76 100644
--- a/src/harfbuzz-impl.h
+++ b/src/harfbuzz-impl.h
@@ -18,7 +18,9 @@
 
 FT_BEGIN_HEADER
 
-#include "ftglue.h"
+#ifndef NULL
+# define NULL ((void *)0)
+#endif
 
 #ifndef FALSE
 # define FALSE 0
@@ -28,6 +30,8 @@ FT_BEGIN_HEADER
 # define TRUE 1
 #endif
 
+#include "ftglue.h"
+
 #define ARRAY_LEN(Array) ((int)(sizeof (Array) / sizeof (Array)[0]))