diff --git a/pkgs/development/python-modules/pyunbound/default.nix b/pkgs/development/python-modules/pyunbound/default.nix
index a8378b5ad22b..0878c20a2c24 100644
--- a/pkgs/development/python-modules/pyunbound/default.nix
+++ b/pkgs/development/python-modules/pyunbound/default.nix
@@ -5,6 +5,8 @@
   openssl,
   expat,
   libevent,
+  bison,
+  flex,
   swig,
   python,
   stdenv,
@@ -17,7 +19,11 @@ buildPythonPackage rec {
 
   patches = unbound.patches or null;
 
-  nativeBuildInputs = [ swig ];
+  nativeBuildInputs = [
+    bison
+    flex
+    swig
+  ];
 
   buildInputs = [
     openssl