diff --git a/extra-builtins.cc b/extra-builtins.cc
index 617807a..c417cb3 100644
--- a/extra-builtins.cc
+++ b/extra-builtins.cc
@@ -27,7 +27,7 @@ static ExtraBuiltinsSettings extraBuiltinsSettings;
 
 static GlobalConfig::Register rp(&extraBuiltinsSettings);
 
-static void extraBuiltins(EvalState & state, const Pos & pos,
+static void extraBuiltins(EvalState & state, const PosIdx pos,
     Value ** _args, Value & v)
 {
     static auto extraBuiltinsFile = absPath(extraBuiltinsSettings.extraBuiltinsFile);
@@ -44,10 +44,10 @@ static void extraBuiltins(EvalState & state, const Pos & pos,
             auto attrs = state.buildBindings(2);
 
             auto sExec = state.symbols.create("exec");
-            attrs.alloc(sExec).mkPrimOp(new PrimOp { .fun = prim_exec, .arity = 1, .name = sExec });
+            attrs.alloc(sExec).mkPrimOp(new PrimOp { .fun = prim_exec, .arity = 1, .name = "exec" });
 
             auto sImportNative = state.symbols.create("importNative");
-            attrs.alloc(sImportNative).mkPrimOp(new PrimOp { .fun = prim_importNative, .arity = 2, .name = sImportNative });
+            attrs.alloc(sImportNative).mkPrimOp(new PrimOp { .fun = prim_importNative, .arity = 2, .name = "importNative" });
 
             arg = state.allocValue();
             arg->mkAttrs(attrs);
@@ -64,7 +64,7 @@ static void extraBuiltins(EvalState & state, const Pos & pos,
 static RegisterPrimOp rp1("__extraBuiltins", 0,
     extraBuiltins);
 
-static void cflags(EvalState & state, const Pos & _pos,
+static void cflags(EvalState & state, const PosIdx _pos,
     Value ** _args, Value & v)
 {
     auto attrs = state.buildBindings(3);