diff --git a/numexpr/necompiler.py b/numexpr/necompiler.py
index f5ef5b7..8a14123 100644
--- a/numexpr/necompiler.py
+++ b/numexpr/necompiler.py
@@ -264,7 +264,7 @@ def __str__(self):
 
 
 _flow_pat = r'[\;\[\:]'
-_dunder_pat = r'__[\w]+__'
+_dunder_pat = r'(^|[^\w])__[\w]+__($|[^\w])'
 _attr_pat = r'\.\b(?!(real|imag|\d*[eE]?[+-]?\d+)\b)'
 _blacklist_re = re.compile(f'{_flow_pat}|{_dunder_pat}|{_attr_pat}')