diff --git a/site_scons/site_tools/cython.py b/site_scons/site_tools/cython.py
index ad53f2831c..45ba797c45 100644
--- a/site_scons/site_tools/cython.py
+++ b/site_scons/site_tools/cython.py
@@ -4,34 +4,35 @@ from SCons.Action import Action
 cythonAction = Action("$CYTHONCOM")
 
 def create_builder(env):
-    try:
-        cython = env['BUILDERS']['Cython']
-    except KeyError:
-        cython = SCons.Builder.Builder(
-                  action = cythonAction,
-                  emitter = {},
-                  suffix = cython_suffix_emitter,
-                  single_source = 1)
-        env['BUILDERS']['Cython'] = cython
-    return cython
+  try:
+    cython = env['BUILDERS']['Cython']
+  except KeyError:
+    cython = SCons.Builder.Builder(
+               action = cythonAction,
+               emitter = {},
+               suffix = cython_suffix_emitter,
+               single_source = 1
+             )
+    env['BUILDERS']['Cython'] = cython
+  return cython
 
 def cython_suffix_emitter(env, source):
-    return "$CYTHONCFILESUFFIX"
+  return "$CYTHONCFILESUFFIX"
 
 def generate(env):
-    env["CYTHON"] = "cythonize"
-    env["CYTHONCOM"] = "$CYTHON $CYTHONFLAGS $SOURCE"
-    env["CYTHONCFILESUFFIX"] = ".cpp"
+  env["CYTHON"] = "cythonize"
+  env["CYTHONCOM"] = "$CYTHON $CYTHONFLAGS $SOURCE"
+  env["CYTHONCFILESUFFIX"] = ".cpp"
 
-    c_file, _ = SCons.Tool.createCFileBuilders(env)
+  c_file, _ = SCons.Tool.createCFileBuilders(env)
 
-    c_file.suffix['.pyx'] = cython_suffix_emitter
-    c_file.add_action('.pyx', cythonAction)
+  c_file.suffix['.pyx'] = cython_suffix_emitter
+  c_file.add_action('.pyx', cythonAction)
 
-    c_file.suffix['.py'] = cython_suffix_emitter
-    c_file.add_action('.py', cythonAction)
+  c_file.suffix['.py'] = cython_suffix_emitter
+  c_file.add_action('.py', cythonAction)
 
-    create_builder(env)
+  create_builder(env)
 
 def exists(env):
   return True