diff --git a/MANIFEST.in b/MANIFEST.in
index b4fde01..a4ca1e7 100644
--- a/MANIFEST.in
+++ b/MANIFEST.in
@@ -1,5 +1,6 @@
 include pyearth/*.c
 include pyearth/*.pxd
+include pyearth/*.pyx
 include pyearth/test/*.txt
 include pyearth/test/*.csv
 include pyearth/test/pathological_data