diff --git a/pyrtlib/tb_spectrum.py b/pyrtlib/tb_spectrum.py
index a43628d3..359ec29e 100644
--- a/pyrtlib/tb_spectrum.py
+++ b/pyrtlib/tb_spectrum.py
@@ -304,10 +304,10 @@ def execute(self, only_bt: bool = True) -> Union[pd.DataFrame, Tuple[pd.DataFram
         """
 
         self._init_linelist()
-        
+
         if self.cloudy and LiqAbsModel.model in ['R98', 'R03']:
             warnings.warn(
-                "Model {} for liquid cloud absorption is outdated. " \
+                "Model {} for liquid cloud absorption is outdated. "
                 "Use the more recent model by Rosenkranz, 2015, from R16 model onwards".format(LiqAbsModel.model), stacklevel=2)
 
         # Set RTE