diff --git a/headers/os/BeBuild.h b/headers/os/BeBuild.h
index 6875361536..7a2aa4ea7f 100644
--- a/headers/os/BeBuild.h
+++ b/headers/os/BeBuild.h
@@ -46,6 +46,8 @@
 
 #ifdef __HAIKU_ARCH_64_BIT
 #	define B_HAIKU_64_BIT				1
+#else
+#	define B_HAIKU_32_BIT				1
 #endif
 
 #ifdef __HAIKU_BEOS_COMPATIBLE