diff --git a/bsp/ls1bdev/SConstruct b/bsp/ls1bdev/SConstruct
index 5a5e89a0eb..d76d68a4a2 100644
--- a/bsp/ls1bdev/SConstruct
+++ b/bsp/ls1bdev/SConstruct
@@ -2,7 +2,10 @@ import os
 import sys
 import rtconfig
 
-RTT_ROOT = os.path.normpath(os.getcwd() + '/../..')
+if os.getenv('RTT_ROOT'):
+    RTT_ROOT = os.getenv('RTT_ROOT')
+else:
+    RTT_ROOT = os.path.normpath(os.getcwd() + '/../..')
 sys.path = sys.path + [os.path.join(RTT_ROOT, 'tools')]
 from building import *