diff --git a/src/libcmd/common-eval-args.cc b/src/libcmd/common-eval-args.cc
index d094989af..263792ec9 100644
--- a/src/libcmd/common-eval-args.cc
+++ b/src/libcmd/common-eval-args.cc
@@ -94,7 +94,8 @@ SourcePath lookupFileArg(EvalState & state, std::string_view s)
     if (isUri(s)) {
         auto storePath = fetchers::downloadTarball(
             state.store, resolveUri(s), "source", false).first.storePath;
-        auto & accessor = state.registerAccessor(makeFSInputAccessor(CanonPath(state.store->toRealPath(storePath))));
+        auto accessor = makeFSInputAccessor(CanonPath(state.store->toRealPath(storePath)));
+        state.registerAccessor(accessor);
         return {accessor, CanonPath::root};
     } else if (s.size() > 2 && s.at(0) == '<' && s.at(s.size() - 1) == '>') {
         Path p(s.substr(1, s.size() - 2));
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 89887823e..497a1e8f5 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -1025,7 +1025,7 @@ void Value::mkStringMove(const char * s, const PathSet & context)
 
 void Value::mkPath(const SourcePath & path)
 {
-    mkPath(&path.accessor, makeImmutableString(path.path.abs()));
+    mkPath(&*path.accessor, makeImmutableString(path.path.abs()));
 }
 
 
@@ -1928,7 +1928,7 @@ void ExprConcatStrings::eval(EvalState & state, Env & env, Value & v)
 
     Value values[es->size()];
     Value * vTmpP = values;
-    InputAccessor * accessor = nullptr;
+    std::shared_ptr<InputAccessor> accessor;
 
     for (auto & [i_pos, i] : *es) {
         Value * vTmp = vTmpP++;
@@ -1947,7 +1947,7 @@ void ExprConcatStrings::eval(EvalState & state, Env & env, Value & v)
         if (first) {
             firstType = vTmp->type();
             if (vTmp->type() == nPath)
-                accessor = &vTmp->path().accessor;
+                accessor = vTmp->path().accessor;
         }
 
         if (firstType == nInt) {
@@ -1984,7 +1984,7 @@ void ExprConcatStrings::eval(EvalState & state, Env & env, Value & v)
     else if (firstType == nPath) {
         if (!context.empty())
             state.throwEvalError(pos, "a string that refers to a store path cannot be appended to a path", env, *this);
-        v.mkPath({.accessor = *accessor, .path = CanonPath(str())});
+        v.mkPath({ref(accessor), CanonPath(str())});
     } else
         v.mkStringMove(c_str(), context);
 }
@@ -2267,7 +2267,7 @@ SourcePath EvalState::coerceToPath(const PosIdx pos, Value & v, PathSet & contex
         auto path = v.str();
         if (path == "" || path[0] != '/')
             throwEvalError(pos, "string '%1%' doesn't represent an absolute path", path);
-        return {*rootFS, CanonPath(path)};
+        return {rootFS, CanonPath(path)};
     }
 
     if (v.type() == nPath)
diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index 56519573b..f9814b501 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -219,7 +219,7 @@ public:
 
     SourcePath rootPath(const Path & path);
 
-    InputAccessor & registerAccessor(ref<InputAccessor> accessor);
+    void registerAccessor(ref<InputAccessor> accessor);
 
     /* Allow access to a path. */
     void allowPath(const Path & path);
diff --git a/src/libexpr/flake/flake.cc b/src/libexpr/flake/flake.cc
index 933dad35a..a5b91b947 100644
--- a/src/libexpr/flake/flake.cc
+++ b/src/libexpr/flake/flake.cc
@@ -266,7 +266,9 @@ static Flake getFlake(
 
     auto [accessor, lockedRef] = resolvedRef.lazyFetch(state.store);
 
-    return readFlake(state, originalRef, resolvedRef, lockedRef, SourcePath {state.registerAccessor(accessor), CanonPath::root}, lockRootPath);
+    state.registerAccessor(accessor);
+
+    return readFlake(state, originalRef, resolvedRef, lockedRef, SourcePath {accessor, CanonPath::root}, lockRootPath);
 }
 
 Flake getFlake(EvalState & state, const FlakeRef & originalRef, bool useRegistries)
diff --git a/src/libexpr/nixexpr.cc b/src/libexpr/nixexpr.cc
index 08478455b..13c3e3587 100644
--- a/src/libexpr/nixexpr.cc
+++ b/src/libexpr/nixexpr.cc
@@ -11,11 +11,9 @@ namespace nix {
 struct SourcePathAdapter : AbstractPos
 {
     SourcePath path;
-    ref<InputAccessor> hack; // FIXME: remove
 
     SourcePathAdapter(SourcePath path)
         : path(std::move(path))
-        , hack(path.accessor.shared_from_this())
     {
     }
 
diff --git a/src/libexpr/nixexpr.hh b/src/libexpr/nixexpr.hh
index 7b732995e..a42a916e2 100644
--- a/src/libexpr/nixexpr.hh
+++ b/src/libexpr/nixexpr.hh
@@ -193,7 +193,7 @@ struct ExprPath : Expr
     ExprPath(SourcePath && _path)
         : path(_path)
     {
-        v.mkPath(&path.accessor, path.path.abs().data());
+        v.mkPath(&*path.accessor, path.path.abs().data());
     }
     Value * maybeThunk(EvalState & state, Env & env) override;
     COMMON_METHODS
diff --git a/src/libexpr/parser.y b/src/libexpr/parser.y
index 14b712f6f..96ee42528 100644
--- a/src/libexpr/parser.y
+++ b/src/libexpr/parser.y
@@ -768,7 +768,7 @@ SourcePath EvalState::findFile(SearchPath & searchPath, const std::string_view p
     }
 
     if (hasPrefix(path, "nix/"))
-        return {*corepkgsFS, CanonPath(path.substr(3))};
+        return {corepkgsFS, CanonPath(path.substr(3))};
 
     debugThrowLastTrace(ThrownError({
         .msg = hintfmt(evalSettings.pureEval
@@ -791,7 +791,8 @@ SourcePath EvalState::findFile(SearchPath & searchPath, const std::string_view p
         try {
             auto storePath = fetchers::downloadTarball(
                 store, resolveUri(elem.second), "source", false).first.storePath;
-            auto & accessor = registerAccessor(makeFSInputAccessor(CanonPath(store->toRealPath(storePath))));
+            auto accessor = makeFSInputAccessor(CanonPath(store->toRealPath(storePath)));
+            registerAccessor(accessor);
             res.emplace(SourcePath {accessor, CanonPath::root});
         } catch (FileTransferError & e) {
             logWarning({
diff --git a/src/libexpr/paths.cc b/src/libexpr/paths.cc
index af5423e84..f366722eb 100644
--- a/src/libexpr/paths.cc
+++ b/src/libexpr/paths.cc
@@ -5,13 +5,12 @@ namespace nix {
 
 SourcePath EvalState::rootPath(const Path & path)
 {
-    return {*rootFS, CanonPath(path)};
+    return {rootFS, CanonPath(path)};
 }
 
-InputAccessor & EvalState::registerAccessor(ref<InputAccessor> accessor)
+void EvalState::registerAccessor(ref<InputAccessor> accessor)
 {
     inputAccessors.emplace(&*accessor, accessor);
-    return *accessor;
 }
 
 }
diff --git a/src/libexpr/primops/fetchTree.cc b/src/libexpr/primops/fetchTree.cc
index 164e387d5..0fc3a809c 100644
--- a/src/libexpr/primops/fetchTree.cc
+++ b/src/libexpr/primops/fetchTree.cc
@@ -186,9 +186,11 @@ static void fetchTree(
     if (params.returnPath) {
         auto [accessor, input2] = input.lazyFetch(state.store);
 
+        state.registerAccessor(accessor);
+
         emitTreeAttrs(
             state,
-            { state.registerAccessor(accessor), CanonPath::root },
+            { accessor, CanonPath::root },
             input2,
             v,
             params.emptyRevFallback,
diff --git a/src/libexpr/primops/patch.cc b/src/libexpr/primops/patch.cc
index a4c0d451b..3268754b5 100644
--- a/src/libexpr/primops/patch.cc
+++ b/src/libexpr/primops/patch.cc
@@ -60,9 +60,11 @@ static void prim_patch(EvalState & state, const PosIdx pos, Value * * args, Valu
     if (!src->path.isRoot())
         throw UnimplementedError("applying patches to a non-root path ('%s') is not yet supported", src->path);
 
-    auto accessor = makePatchingInputAccessor(ref(src->accessor.shared_from_this()), patches);
+    auto accessor = makePatchingInputAccessor(src->accessor, patches);
 
-    v.mkPath(SourcePath { state.registerAccessor(accessor), src->path });
+    state.registerAccessor(accessor);
+
+    v.mkPath(SourcePath{accessor, src->path});
 }
 
 static RegisterPrimOp primop_patch({
diff --git a/src/libexpr/value.hh b/src/libexpr/value.hh
index 139bfaa5d..5a8d6413b 100644
--- a/src/libexpr/value.hh
+++ b/src/libexpr/value.hh
@@ -415,7 +415,10 @@ public:
     SourcePath path() const
     {
         assert(internalType == tPath);
-        return SourcePath { .accessor = *_path.accessor, .path = CanonPath(CanonPath::unchecked_t(), _path.path) };
+        return SourcePath {
+            .accessor = ref(_path.accessor->shared_from_this()),
+            .path = CanonPath(CanonPath::unchecked_t(), _path.path)
+        };
     }
 
     std::string_view str() const
diff --git a/src/libfetchers/input-accessor.cc b/src/libfetchers/input-accessor.cc
index c9472d9a8..a335f1e10 100644
--- a/src/libfetchers/input-accessor.cc
+++ b/src/libfetchers/input-accessor.cc
@@ -290,11 +290,11 @@ SourcePath SourcePath::resolveSymlinks() const
     for (auto & component : path) {
         res.push(component);
         while (true) {
-            if (auto st = accessor.maybeLstat(res)) {
+            if (auto st = accessor->maybeLstat(res)) {
                 if (!linksAllowed--)
                     throw Error("infinite symlink recursion in path '%s'", path);
                 if (st->type != InputAccessor::tSymlink) break;
-                auto target = accessor.readLink(res);
+                auto target = accessor->readLink(res);
                 if (hasPrefix(target, "/"))
                     res = CanonPath(target);
                 else {
diff --git a/src/libfetchers/input-accessor.hh b/src/libfetchers/input-accessor.hh
index ceac4f356..46ae48b2a 100644
--- a/src/libfetchers/input-accessor.hh
+++ b/src/libfetchers/input-accessor.hh
@@ -92,7 +92,7 @@ ref<InputAccessor> makePatchingInputAccessor(
 
 struct SourcePath
 {
-    InputAccessor & accessor;
+    ref<InputAccessor> accessor;
     CanonPath path;
 
     std::string_view baseName() const;
@@ -100,30 +100,30 @@ struct SourcePath
     SourcePath parent() const;
 
     std::string readFile() const
-    { return accessor.readFile(path); }
+    { return accessor->readFile(path); }
 
     bool pathExists() const
-    { return accessor.pathExists(path); }
+    { return accessor->pathExists(path); }
 
     InputAccessor::Stat lstat() const
-    { return accessor.lstat(path); }
+    { return accessor->lstat(path); }
 
     std::optional<InputAccessor::Stat> maybeLstat() const
-    { return accessor.maybeLstat(path); }
+    { return accessor->maybeLstat(path); }
 
     InputAccessor::DirEntries readDirectory() const
-    { return accessor.readDirectory(path); }
+    { return accessor->readDirectory(path); }
 
     std::string readLink() const
-    { return accessor.readLink(path); }
+    { return accessor->readLink(path); }
 
     void dumpPath(
         Sink & sink,
         PathFilter & filter = defaultPathFilter) const
-    { return accessor.dumpPath(path, sink, filter); }
+    { return accessor->dumpPath(path, sink, filter); }
 
     std::string to_string() const
-    { return accessor.showPath(path); }
+    { return accessor->showPath(path); }
 
     SourcePath operator + (const CanonPath & x) const
     { return {accessor, path + x}; }
diff --git a/src/libutil/ref.hh b/src/libutil/ref.hh
index bf26321db..7d38b059c 100644
--- a/src/libutil/ref.hh
+++ b/src/libutil/ref.hh
@@ -83,6 +83,11 @@ public:
         return p != other.p;
     }
 
+    bool operator < (const ref<T> & other) const
+    {
+        return p < other.p;
+    }
+
 private:
 
     template<typename T2, typename... Args>