diff --git a/bitbake/lib/bb/data_smart.py b/bitbake/lib/bb/data_smart.py
index 297a2f45b4..c342adaa0a 100644
--- a/bitbake/lib/bb/data_smart.py
+++ b/bitbake/lib/bb/data_smart.py
@@ -43,6 +43,7 @@ __setvar_regexp__ = re.compile(r'(?P<base>.*?)(?P<keyword>_append|_prepend|_remo
 __expand_var_regexp__ = re.compile(r"\${[^{}@\n\t :]+}")
 __expand_python_regexp__ = re.compile(r"\${@.+?}")
 __whitespace_split__ = re.compile(r'(\s)')
+__override_regexp__ = re.compile(r'[a-z0-9]+')
 
 def infer_caller_details(loginfo, parent = False, varval = True):
     """Save the caller the trouble of specifying everything."""
@@ -597,7 +598,7 @@ class DataSmart(MutableMapping):
         # aka pay the cookie monster
         override = var[var.rfind('_')+1:]
         shortvar = var[:var.rfind('_')]
-        while override and override.islower():
+        while override and __override_regexp__.match(override):
             if shortvar not in self.overridedata:
                 self.overridedata[shortvar] = []
             if [var, override] not in self.overridedata[shortvar]: