diff --git a/build.py b/build.py
index fd26163..fa2b3e4 100644
--- a/build.py
+++ b/build.py
@@ -6,14 +6,14 @@
 # define the extension module
 src_dir = "src/"
 exact_cover_impl = Extension(
-    'exact_cover_impl',
+    "exact_cover_impl",
     sources=[
-        src_dir + 'exact_cover.c',
-        src_dir + 'dlx.c',
-        src_dir + 'sparse_matrix.c',
-        src_dir + 'quad_linked_list.c'
+        src_dir + "exact_cover.c",
+        src_dir + "dlx.c",
+        src_dir + "sparse_matrix.c",
+        src_dir + "quad_linked_list.c",
     ],
-    include_dirs=[src_dir, numpy.get_include()]
+    include_dirs=[src_dir, numpy.get_include()],
 )