diff --git a/nnpdf_data/nnpdf_data/commondata/CMS_WPWM_7TEV_MUON/filter.py b/nnpdf_data/nnpdf_data/commondata/CMS_WPWM_7TEV_MUON/filter.py
index c723f9c28e..ea2fed3f6d 100644
--- a/nnpdf_data/nnpdf_data/commondata/CMS_WPWM_7TEV_MUON/filter.py
+++ b/nnpdf_data/nnpdf_data/commondata/CMS_WPWM_7TEV_MUON/filter.py
@@ -160,7 +160,7 @@ def read_corrmatrix(nb_datapoints: int) -> np.ndarray:
 
     """
     corrmat = pd.read_csv(
-        "./rawdata/covmat.corr", names=[f'{i}' for i in range(nb_datapoints)], delim_whitespace=True
+        "./rawdata/covmat.corr", names=[f'{i}' for i in range(nb_datapoints)], sep=r'\s+'
     )
     return corrmat.iloc[:, :].values