diff --git a/build/jam/BuildSetup b/build/jam/BuildSetup
index 2d2d4f2989..ee5122611d 100644
--- a/build/jam/BuildSetup
+++ b/build/jam/BuildSetup
@@ -545,7 +545,7 @@ if $(TARGET_PLATFORM) = haiku {
 	TARGET_GCC_LIBGCC			= $(HAIKU_GCC_LIBGCC) ;
 	TARGET_GCC_LIBGCC_OBJECTS	= $(HAIKU_GCC_LIBGCC_OBJECTS) ;
 
-	TARGET_BOOT_PLATFORM		= $(HAIKU_BOOT_PLATFORM) ;
+	TARGET_BOOT_PLATFORM		?= $(HAIKU_BOOT_PLATFORM) ;
 
 	TARGET_LIBRARY_NAME_MAP		= HAIKU_LIBRARY_NAME_MAP ;