diff --git a/ogs_merge/ogs_merge b/ogs_merge/ogs_merge
index 96f7002..bb72c43 100644
--- a/ogs_merge/ogs_merge
+++ b/ogs_merge/ogs_merge
@@ -489,7 +489,7 @@ class OgsMerger():
             # FIXME CDS could be more appropriate (or maybe not...)
             if not li.startswith("#") and cols[2] == 'exon':
                 cols[8] = re.sub(r'ID=([a-zA-Z0-9]+)', r'exID=\1', cols[8])  # remove already set id
-                cols[8] = re.sub(r'Parent=([a-zA-Z0-9]+)([\.0-9]+)?([-_]R[A-Z]+)?(,[a-zA-Z0-9\.\-_]*)?', r'ID=\1', cols[8])  # generate a fake id based on Parent + remove multiple parents (ie when an exon is part of multiple isoforms)
+                cols[8] = re.sub(r'Parent=([a-zA-Z0-9_]+)([\.0-9]+)?([-_]R[A-Z]+)?(,[a-zA-Z0-9\.\-_]*)?', r'ID=\1', cols[8])  # generate a fake id based on Parent + remove multiple parents (ie when an exon is part of multiple isoforms)
                 cols[8] = cols[8].rstrip(";")  # gff2bed doesn't like trailing ;
                 print('\t'.join(cols), file=base_gff_out)
         base_gff_out.close()