diff --git a/pkgs/tools/security/fierce/default.nix b/pkgs/tools/security/fierce/default.nix
index 5d12a0008158..13146c3373e7 100644
--- a/pkgs/tools/security/fierce/default.nix
+++ b/pkgs/tools/security/fierce/default.nix
@@ -11,8 +11,16 @@ python3.pkgs.buildPythonApplication rec {
     sha256 = "11yaz8ap9swx95j3wpqh0b6jhw6spqgfnsyn1liw9zqi4jwgiax7";
   };
 
+  postPatch = ''
+    substituteInPlace requirements.txt --replace 'dnspython==1.16.0' 'dnspython'
+  '';
+
   propagatedBuildInputs = [ python3.pkgs.dns ];
 
+  # tests require network access
+  doCheck = false;
+  pythonImportsCheck = [ "fierce" ];
+
   meta = with stdenv.lib; {
     homepage = "https://github.com/mschwager/fierce";
     description = "DNS reconnaissance tool for locating non-contiguous IP space";