diff --git a/doc/utils/converters/lammpsdoc/doc_anchor_check.py b/doc/utils/converters/lammpsdoc/doc_anchor_check.py
index 2eeed9077..a072ab1a6 100755
--- a/doc/utils/converters/lammpsdoc/doc_anchor_check.py
+++ b/doc/utils/converters/lammpsdoc/doc_anchor_check.py
@@ -1,60 +1,60 @@
 #! /usr/bin/env python3
 # LAMMPS Documentation Utilities
 #
 # Scan for duplicate anchor labels in documentation files
 #
 # Copyright (C) 2017 Richard Berger
 #
 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
 # the Free Software Foundation, either version 3 of the License, or
 # (at your option) any later version.
 #
 # This program is distributed in the hope that it will be useful,
 # but WITHOUT ANY WARRANTY; without even the implied warranty of
 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 # GNU General Public License for more details.
 #
 # You should have received a copy of the GNU General Public License
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 import re
 import sys
 import argparse
 
 def main():
     parser = argparse.ArgumentParser(description='scan for duplicate anchor labels in documentation files')
     parser.add_argument('files',  metavar='file', nargs='+', help='one or more files to scan')
     parsed_args = parser.parse_args()
 
     anchor_pattern = re.compile(r'^:link\(([^,\)]*)\)')
     anchors = {}
 
     for filename in parsed_args.files:
         with open(filename, 'rt') as f:
             for line_number, line in enumerate(f):
                 m = anchor_pattern.match(line)
                 if m:
                     label = m.group(1)
                     if label in anchors:
-                        anchors[label].append((filename, line_number))
+                        anchors[label].append((filename, line_number+1))
                     else:
-                        anchors[label] = [(filename, line_number)]
+                        anchors[label] = [(filename, line_number+1)]
 
     count = 0
 
     for label in sorted(anchors.keys()):
         if len(anchors[label]) > 1:
             print(label)
             count += 1
             for filename, line_number in anchors[label]:
                 print(" - %s:%d" % (filename, line_number))
 
 
     if count > 0:
         print("Found %d anchor label errors." % count)
         sys.exit(1)
     else:
         print("No anchor label errors.")
 
 if __name__ == "__main__":
     main()