diff --git a/dist/tools/mkconstfs/mkconstfs.py b/dist/tools/mkconstfs/mkconstfs.py
index bda89c76d888ac18f67530d918165302d80abd04..1b56492546ee0dbe7f97682e15349263b9579b47 100755
--- a/dist/tools/mkconstfs/mkconstfs.py
+++ b/dist/tools/mkconstfs/mkconstfs.py
@@ -5,6 +5,8 @@ import os
 import sys
 
 FILE_TYPE = "static const uint8_t"
+FILES = []
+
 
 def mkconstfs(root_path, mount_point, constfs_name):
     print("/* This file was automatically generated by mkconstfs */")
@@ -20,7 +22,7 @@ def mkconstfs(root_path, mount_point, constfs_name):
 
     print("\nstatic const constfs_file_t _files[] = {")
 
-    for mangled_name, target_name, _ in files:
+    for mangled_name, target_name, _ in FILES:
         print("    {")
         print("    .path = \"%s\"," % target_name)
         print("    .data = %s," % mangled_name)
@@ -41,12 +43,14 @@ vfs_mount_t %s = {
 };
     """ % (constfs_name, mount_point))
 
+
 def mangle_name(fname):
     fname = fname.replace("/", "__")
     fname = fname.replace(".", "__")
 
     return fname
 
+
 def print_file_data(local_fname, target_fname):
     mangled_name = mangle_name(target_fname)
     print(FILE_TYPE, mangled_name, "[] = {", end="")
@@ -63,17 +67,16 @@ def print_file_data(local_fname, target_fname):
             else:
                 print(", ", end="")
             nread += 1
-            print ("0x" + codecs.encode(byte, 'hex').decode('ascii'), end="")
+            print("0x" + codecs.encode(byte, 'hex').decode('ascii'), end="")
             # Do stuff with byte.
             byte = f.read(1)
 
     print("\n};")
 
-    files.append((mangled_name, target_fname, nread))
+    FILES.append((mangled_name, target_fname, nread))
 
-files = []
 
-if __name__=="__main__":
+if __name__ == "__main__":
     mountpoint = "/"
     constfs_name = "_constfs"