diff --git a/contrib/devtools/fix-copyright-headers.py b/contrib/devtools/fix-copyright-headers.py
index 31a81ae4f..54836bd83 100755
--- a/contrib/devtools/fix-copyright-headers.py
+++ b/contrib/devtools/fix-copyright-headers.py
@@ -1,5 +1,5 @@
-#!/usr/bin/env python
-'''
+#!/usr/bin/env python3
+"""
 Run this script to update all the copyright headers of files
 that were changed this year.
 
@@ -10,37 +10,58 @@ For example:
 it will change it to
 
 // Copyright (c) 2009-2015 The Bitcoin Core developers
-'''
-import os
+"""
+import subprocess
 import time
 import re
 
-year = time.gmtime()[0]
-CMD_GIT_DATE = 'git log --format=%%ad --date=short -1 %s | cut -d"-" -f 1'
-CMD_REGEX= "perl -pi -e 's/(20\d\d)(?:-20\d\d)? The Bitcoin/$1-%s The Bitcoin/' %s"
-REGEX_CURRENT= re.compile("%s The Bitcoin" % year)
-CMD_LIST_FILES= "find %s | grep %s"
+CMD_GIT_LIST_FILES = ['git', 'ls-files']
+CMD_GIT_DATE = ['git', 'log', '--format=%ad', '--date=short', '-1']
+CMD_PERL_REGEX = ['perl', '-pi', '-e']
+REGEX_TEMPLATE = 's/(20\\d\\d)(?:-20\\d\\d)? The Bitcoin/$1-%s The Bitcoin/'
 
-FOLDERS = ["./qa", "./src"]
+FOLDERS = ["qa/", "src/"]
 EXTENSIONS = [".cpp",".h", ".py"]
 
+
 def get_git_date(file_path):
-  r = os.popen(CMD_GIT_DATE % file_path)
-  for l in r:
-    # Result is one line, so just return
-    return l.replace("\n","")
-  return ""
-
-n=1
-for folder in FOLDERS:
-  for extension in EXTENSIONS:
-    for file_path in os.popen(CMD_LIST_FILES % (folder, extension)):
-      file_path = os.getcwd() + file_path[1:-1]
-      if file_path.endswith(extension):
-        git_date = get_git_date(file_path)
-        if str(year) == git_date:
-          # Only update if current year is not found
-          if REGEX_CURRENT.search(open(file_path, "r").read()) is None:
-            print n,"Last git edit", git_date, "-", file_path
-            os.popen(CMD_REGEX % (year,file_path))
+    d = subprocess.run(CMD_GIT_DATE + [file_path],
+                       stdout=subprocess.PIPE,
+                       check=True,
+                       universal_newlines=True).stdout
+    # yyyy-mm-dd
+    return d.split('-')[0]
+
+
+def skip_file(file_path):
+    for ext in EXTENSIONS:
+        if file_path.endswith(ext):
+            return False
+    else:
+        return True
+
+if __name__ == "__main__":
+    year = str(time.gmtime()[0])
+    regex_current = re.compile("%s The Bitcoin" % year)
+    n = 1
+    for folder in FOLDERS:
+        for file_path in subprocess.run(
+            CMD_GIT_LIST_FILES + [folder],
+            stdout=subprocess.PIPE,
+            check=True,
+            universal_newlines=True
+        ).stdout.split("\n"):
+            if skip_file(file_path):
+                # print(file_path, "(skip)")
+                continue
+            git_date = get_git_date(file_path)
+            if not year == git_date:
+                # print(file_path, year, "(skip)")
+                continue
+            if regex_current.search(open(file_path, "r").read()) is not None:
+                # already up to date
+                # print(file_path, year, "(skip)")
+                continue
+            print(n, file_path, "(update to %s)" % year)
+            subprocess.run(CMD_PERL_REGEX + [REGEX_TEMPLATE % year, file_path], check=True)
             n = n + 1