diff --git a/pkgs/lumpy.nix b/pkgs/lumpy.nix
index 004ff0b..04be231 100644
--- a/pkgs/lumpy.nix
+++ b/pkgs/lumpy.nix
@@ -39,7 +39,7 @@ stdenv.mkDerivation rec {
     automake
     zlib
     curl
-    (python2.withPackages (packages: with packages; [ python2Packages.numpy pysam ]))
+    (python2.withPackages (packages: with packages; [ python2Packages.numpy python2Packages.pysam ]))
     hexdump
     sambamba
     samblaster