diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index 47d8076b1..5b2f7e8b7 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -4058,18 +4058,6 @@ static RegisterPrimOp primop_splitVersion({
 RegisterPrimOp::PrimOps * RegisterPrimOp::primOps;
 
 
-RegisterPrimOp::RegisterPrimOp(std::string name, size_t arity, PrimOpFun fun)
-{
-    if (!primOps) primOps = new PrimOps;
-    primOps->push_back({
-        .name = name,
-        .args = {},
-        .arity = arity,
-        .fun = fun,
-    });
-}
-
-
 RegisterPrimOp::RegisterPrimOp(Info && info)
 {
     if (!primOps) primOps = new PrimOps;
diff --git a/src/libexpr/primops.hh b/src/libexpr/primops.hh
index 4ae73fe1f..73b7b866c 100644
--- a/src/libexpr/primops.hh
+++ b/src/libexpr/primops.hh
@@ -28,11 +28,6 @@ struct RegisterPrimOp
      * will get called during EvalState initialization, so there
      * may be primops not yet added and builtins is not yet sorted.
      */
-    RegisterPrimOp(
-        std::string name,
-        size_t arity,
-        PrimOpFun fun);
-
     RegisterPrimOp(Info && info);
 };
 
diff --git a/tests/plugins/plugintest.cc b/tests/plugins/plugintest.cc
index 04b791021..e02fd68d5 100644
--- a/tests/plugins/plugintest.cc
+++ b/tests/plugins/plugintest.cc
@@ -21,4 +21,8 @@ static void prim_anotherNull (EvalState & state, const PosIdx pos, Value ** args
         v.mkBool(false);
 }
 
-static RegisterPrimOp rp("anotherNull", 0, prim_anotherNull);
+static RegisterPrimOp rp({
+    .name = "anotherNull",
+    .arity = 0,
+    .fun = prim_anotherNull,
+});