diff --git a/pkgs/by-name/kn/knot-dns/package.nix b/pkgs/by-name/kn/knot-dns/package.nix
index fba4e166463d..e3fc0b3657f0 100644
--- a/pkgs/by-name/kn/knot-dns/package.nix
+++ b/pkgs/by-name/kn/knot-dns/package.nix
@@ -64,6 +64,7 @@ stdenv.mkDerivation rec {
   # FIXME: sphinx is needed for now to get man-pages
   nativeBuildInputs = [
     pkg-config
+    protobufc # dnstap support
     autoreconfHook
     sphinx
   ];
@@ -94,6 +95,7 @@ stdenv.mkDerivation rec {
   ++ lib.optional stdenv.hostPlatform.isDarwin zlib; # perhaps due to gnutls
 
   enableParallelBuilding = true;
+  strictDeps = true;
 
   CFLAGS = [
     "-O2"