diff --git a/src/libexpr/attr-set.hh b/src/libexpr/attr-set.hh
index cad9743ea..1e6c548c6 100644
--- a/src/libexpr/attr-set.hh
+++ b/src/libexpr/attr-set.hh
@@ -73,18 +73,6 @@ public:
         return nullptr;
     }
 
-    Attr & need(const Symbol & name, const Pos & pos = noPos)
-    {
-        auto a = get(name);
-        if (!a)
-            throw Error({
-                .msg = hintfmt("attribute '%s' missing", name),
-                .errPos = pos
-            });
-
-        return *a;
-    }
-
     iterator begin() { return &attrs[0]; }
     iterator end() { return &attrs[size_]; }
 
diff --git a/src/nix/bundle.cc b/src/nix/bundle.cc
index 81fb8464a..ee91e8ed0 100644
--- a/src/nix/bundle.cc
+++ b/src/nix/bundle.cc
@@ -110,8 +110,10 @@ struct CmdBundle : InstallableCommand
         auto outPathS = store->printStorePath(outPath);
 
         if (!outLink) {
-            auto &attr = vRes->attrs->need(evalState->sName);
-            outLink = evalState->forceStringNoCtx(*attr.value,*attr.pos);
+            auto * attr = vRes->attrs->get(evalState->sName);
+            if (!attr)
+                throw Error("attribute 'name' missing");
+            outLink = evalState->forceStringNoCtx(*attr->value, *attr->pos);
         }
 
         // TODO: will crash if not a localFSStore?
diff --git a/src/nix/prefetch.cc b/src/nix/prefetch.cc
index f2dd44ba4..ce3288dc1 100644
--- a/src/nix/prefetch.cc
+++ b/src/nix/prefetch.cc
@@ -199,11 +199,13 @@ static int main_nix_prefetch_url(int argc, char * * argv)
             state->forceAttrs(v, noPos);
 
             /* Extract the URL. */
-            auto & attr = v.attrs->need(state->symbols.create("urls"));
-            state->forceList(*attr.value, noPos);
-            if (attr.value->listSize() < 1)
+            auto * attr = v.attrs->get(state->symbols.create("urls"));
+            if (!attr)
+                throw Error("attribute 'urls' missing");
+            state->forceList(*attr->value, noPos);
+            if (attr->value->listSize() < 1)
                 throw Error("'urls' list is empty");
-            url = state->forceString(*attr.value->listElems()[0]);
+            url = state->forceString(*attr->value->listElems()[0]);
 
             /* Extract the hash mode. */
             auto attr2 = v.attrs->get(state->symbols.create("outputHashMode"));