diff --git a/bitbake/lib/bb/data_smart.py b/bitbake/lib/bb/data_smart.py
index 7dc1c68709..7b09af5cf1 100644
--- a/bitbake/lib/bb/data_smart.py
+++ b/bitbake/lib/bb/data_smart.py
@@ -39,7 +39,7 @@ from bb.COW  import COWDictBase
 logger = logging.getLogger("BitBake.Data")
 
 __setvar_keyword__ = ["_append", "_prepend", "_remove"]
-__setvar_regexp__ = re.compile('(?P<base>.*?)(?P<keyword>_append|_prepend|_remove)(_(?P<add>.*))?$')
+__setvar_regexp__ = re.compile('(?P<base>.*?)(?P<keyword>_append|_prepend|_remove)(_(?P<add>[^A-Z]*))?$')
 __expand_var_regexp__ = re.compile(r"\${[^{}@\n\t :]+}")
 __expand_python_regexp__ = re.compile(r"\${@.+?}")