diff --git a/pkgs/development/python-modules/scapy/default.nix b/pkgs/development/python-modules/scapy/default.nix
index 970d355fff06b8..dede907418e3f2 100644
--- a/pkgs/development/python-modules/scapy/default.nix
+++ b/pkgs/development/python-modules/scapy/default.nix
@@ -44,10 +44,11 @@ buildPythonPackage rec {
     substituteInPlace scapy/data.py --replace "/opt/wireshark" "${wireshark}"
   '';
 
+  buildInputs = lib.optional withVoipSupport sox;
+
   propagatedBuildInputs = [ pycrypto ecdsa ]
     ++ lib.optionals withOptionalDeps [ tcpdump ipython ]
     ++ lib.optional withCryptography cryptography
-    ++ lib.optional withVoipSupport sox
     ++ lib.optional withPlottingSupport matplotlib
     ++ lib.optionals withGraphicsSupport [ pyx texliveBasic graphviz imagemagick ];