diff --git a/x10_any.py b/x10_any.py
index <HASH>..<HASH> 100644
--- a/x10_any.py
+++ b/x10_any.py
@@ -18,6 +18,8 @@ class X10InvalidHouseCode(X10BaseException):
 def normalize_housecode(house_code):
     if house_code is None:
         raise X10InvalidHouseCode('%r is not a valid house code' % house_code)
+    if len(house_code) != 1:
+        raise X10InvalidHouseCode('%r is not a valid house code' % house_code)
     house_code = house_code.upper()
     if not ('A' <= house_code <= 'P'):
         raise X10InvalidHouseCode('%r is not a valid house code' % house_code)
Validation of house code ready for larger testing/use