diff --git a/lib/stdbool.in.h b/lib/stdbool.in.h
index 2784a50..01c018b 100644
--- a/lib/stdbool.in.h
+++ b/lib/stdbool.in.h
@@ -58,7 +58,7 @@
 
 /* BeOS <sys/socket.h> already #defines false 0, true 1.  We use the same
    definitions below, but temporarily we have to #undef them.  */
-#ifdef __BEOS__
+#if defined __BEOS__ && !defined __HAIKU__
 # include <OS.h> /* defines bool but not _Bool */
 # undef false
 # undef true
@@ -73,7 +73,7 @@
    (see ISO C 99 6.7.2.2.(4)); however, '_Bool' must promote to 'int'
    (see ISO C 99 6.3.1.1.(2)).  So we add a negative value to the
    enum; this ensures that '_Bool' promotes to 'int'.  */
-#if defined __cplusplus || defined __BEOS__
+#if defined __cplusplus || (defined __BEOS__ && !defined __HAIKU__)
   /* A compiler known to have 'bool'.  */
   /* If the compiler already has both 'bool' and '_Bool', we can assume they
      are the same types.  */