diff --git a/resources/master_data/scripts/master_formula.py b/resources/master_data/scripts/master_formula.py
index 32ae615f..ec47a7f4 100644
--- a/resources/master_data/scripts/master_formula.py
+++ b/resources/master_data/scripts/master_formula.py
@@ -129,10 +129,9 @@ class _Parser:
             elif depth == 0 and ch == ",":
                 break
             elif depth == 0 and ch == "." and not self.s[self.i + 1 : self.i + 2].isdigit():
-                around = self.s[self.i - 1 : self.i] + self.s[self.i + 1 : self.i + 2]
-                if not (
-                    around.isascii() and around.isalpha() and len(around) == 2
-                ):  # 「K.P」「T.S」 는 열쇠 글자
+                # 「K.P」「T.S」 처럼 영문자 사이 점은 열쇠 글자
+                around = self.s[self.i - 1 : self.i + 2 : 2]
+                if not (len(around) == 2 and around.isascii() and around.isalpha()):
                     break
             elif depth == 0 and re.match(r"\s[-+*/<>=!]", self.s[self.i : self.i + 2]):
                 break