diff --git a/SConstruct b/SConstruct
index e27f8eae367..dbeabb5c2ef 100644
--- a/SConstruct
+++ b/SConstruct
@@ -111,6 +111,11 @@ btools.print_targets(B.targets, B.bc)
 
 # handling cmd line arguments & config file
 
+# bitness stuff
+tempbitness = int(B.arguments.get('BF_BITNESS', bitness)) # default to bitness found as per starting python
+if tempbitness in (32, 64): # only set if 32 or 64 has been given
+    bitness = int(tempbitness)
+
 # first check cmdline for toolset and we create env to work on
 quickie = B.arguments.get('BF_QUICK', None)
 quickdebug = B.arguments.get('BF_QUICKDEBUG', None)
diff --git a/build_files/scons/tools/btools.py b/build_files/scons/tools/btools.py
index b20f3ede68d..66f0494b1dd 100644
--- a/build_files/scons/tools/btools.py
+++ b/build_files/scons/tools/btools.py
@@ -159,7 +159,7 @@ def validate_arguments(args, bc):
             'BF_BSC', 'BF_CONFIG',
             'BF_PRIORITYLIST', 'BF_BUILDINFO','CC', 'CXX', 'BF_QUICKDEBUG',
             'BF_LISTDEBUG', 'LCGDIR', 'BF_X264_CONFIG', 'BF_XVIDCORE_CONFIG',
-            'BF_UNIT_TEST']
+            'BF_UNIT_TEST', 'BF_BITNESS']
 
     okdict = {}