diff --git a/pix2tex/gui.py b/pix2tex/gui.py
index b0dc2a3..32ede8c 100644
--- a/pix2tex/gui.py
+++ b/pix2tex/gui.py
@@ -25,7 +25,7 @@
 ACCEPTED_IMAGE_SUFFIX = ['png', 'jpg', 'jpeg']
 
 def to_sympy(latex):
-    normalized = re.sub(r'operatorname\*{(\w+)}', '\g<1>', latex)
+    normalized = re.sub(r'operatorname\*{(\w+)}', r'\g<1>', latex)
     sympy_expr = latex2sympy(f'${normalized}$')
     return sympy_expr
 
@@ -515,4 +515,4 @@ def main(arguments):
             os.environ['QTWEBENGINE_DISABLE_SANDBOX'] = '1'
         app = QApplication(sys.argv)
         ex = App(arguments)
-        sys.exit(app.exec())
\ No newline at end of file
+        sys.exit(app.exec())