diff --git a/jass_preprocessing/map_reference.py b/jass_preprocessing/map_reference.py
index 8210e0a9a9a45bcc240ea9498553d6d21ad9ebf2..1949b1bbcfdbcea27b5f43ba43167aa91e484ff9 100644
--- a/jass_preprocessing/map_reference.py
+++ b/jass_preprocessing/map_reference.py
@@ -82,7 +82,7 @@ def map_on_ref_panel(gw_df , ref_panel, index_type="rs-number"):
         else:
             raise ValueError("index_type can take only two values: 'rs-number' or 'positional'")
 
-    if (("pos" in merge_GWAS.columns) and ("POS" in merge_GWAS.columns))
+    if (("pos" in merge_GWAS.columns) and ("POS" in merge_GWAS.columns)):
         if (merge_GWAS.pos == merge_GWAS.POS).mean()> 0.95):
             merge_GWAS = merge_GWAS.loc[(merge_GWAS.pos == merge_GWAS.POS)]
         else: