diff --git a/src/libcmd/installables.cc b/src/libcmd/installables.cc
index b93c7f7e8..0d42a62cc 100644
--- a/src/libcmd/installables.cc
+++ b/src/libcmd/installables.cc
@@ -21,7 +21,6 @@
 #include "url.hh"
 #include "registry.hh"
 #include "build-result.hh"
-#include "fs-input-accessor.hh"
 
 #include <regex>
 #include <queue>
@@ -147,7 +146,7 @@ MixFlakeOptions::MixFlakeOptions()
         .category = category,
         .labels = {"flake-lock-path"},
         .handler = {[&](std::string lockFilePath) {
-            lockFlags.referenceLockFilePath = getUnfilteredRootPath(CanonPath(absPath(lockFilePath)));
+            lockFlags.referenceLockFilePath = {makeFSSourceAccessor(), CanonPath(absPath(lockFilePath))};
         }},
         .completer = completePath
     });
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index fbd846d14..6fd60084d 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -15,7 +15,6 @@
 #include "function-trace.hh"
 #include "profiles.hh"
 #include "print.hh"
-#include "fs-input-accessor.hh"
 #include "filtering-input-accessor.hh"
 #include "memory-source-accessor.hh"
 #include "signals.hh"
@@ -400,14 +399,14 @@ EvalState::EvalState(
     , emptyBindings(0)
     , rootFS(
         evalSettings.restrictEval || evalSettings.pureEval
-        ? ref<SourceAccessor>(AllowListInputAccessor::create(makeFSInputAccessor(), {},
+        ? ref<SourceAccessor>(AllowListInputAccessor::create(makeFSSourceAccessor(), {},
             [](const CanonPath & path) -> RestrictedPathError {
                 auto modeInformation = evalSettings.pureEval
                     ? "in pure evaluation mode (use '--impure' to override)"
                     : "in restricted mode";
                 throw RestrictedPathError("access to absolute path '%1%' is forbidden %2%", path, modeInformation);
             }))
-        : makeFSInputAccessor())
+        : makeFSSourceAccessor())
     , corepkgsFS(make_ref<MemorySourceAccessor>())
     , internalFS(make_ref<MemorySourceAccessor>())
     , derivationInternal{corepkgsFS->addFile(
diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index a3ccc9771..109127d1d 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -15,7 +15,6 @@
 #include "value-to-json.hh"
 #include "value-to-xml.hh"
 #include "primops.hh"
-#include "fs-input-accessor.hh"
 #include "fetch-to-store.hh"
 
 #include <boost/container/small_vector.hpp>
diff --git a/src/libfetchers/fetch-to-store.cc b/src/libfetchers/fetch-to-store.cc
index 398286065..c105fe1fc 100644
--- a/src/libfetchers/fetch-to-store.cc
+++ b/src/libfetchers/fetch-to-store.cc
@@ -14,7 +14,7 @@ StorePath fetchToStore(
     RepairFlag repair)
 {
     // FIXME: add an optimisation for the case where the accessor is
-    // an FSInputAccessor pointing to a store path.
+    // a `PosixSourceAccessor` pointing to a store path.
 
     std::optional<fetchers::Attrs> cacheKey;
 
diff --git a/src/libfetchers/fs-input-accessor.cc b/src/libfetchers/fs-input-accessor.cc
deleted file mode 100644
index bd4e4e2cd..000000000
--- a/src/libfetchers/fs-input-accessor.cc
+++ /dev/null
@@ -1,34 +0,0 @@
-#include "fs-input-accessor.hh"
-#include "posix-source-accessor.hh"
-#include "store-api.hh"
-
-namespace nix {
-
-ref<SourceAccessor> makeFSInputAccessor()
-{
-    return make_ref<PosixSourceAccessor>();
-}
-
-ref<SourceAccessor> makeFSInputAccessor(std::filesystem::path root)
-{
-    return make_ref<PosixSourceAccessor>(std::move(root));
-}
-
-ref<SourceAccessor> makeStorePathAccessor(
-    ref<Store> store,
-    const StorePath & storePath)
-{
-    // FIXME: should use `store->getFSAccessor()`
-    auto root = std::filesystem::path { store->toRealPath(storePath) };
-    auto accessor = makeFSInputAccessor(root);
-    accessor->setPathDisplay(root.string());
-    return accessor;
-}
-
-SourcePath getUnfilteredRootPath(CanonPath path)
-{
-    static auto rootFS = makeFSInputAccessor();
-    return {rootFS, path};
-}
-
-}
diff --git a/src/libfetchers/git-utils.cc b/src/libfetchers/git-utils.cc
index 5657a6b4f..a91587cb4 100644
--- a/src/libfetchers/git-utils.cc
+++ b/src/libfetchers/git-utils.cc
@@ -1,5 +1,4 @@
 #include "git-utils.hh"
-#include "fs-input-accessor.hh"
 #include "cache.hh"
 #include "finally.hh"
 #include "processes.hh"
@@ -948,7 +947,7 @@ ref<SourceAccessor> GitRepoImpl::getAccessor(const WorkdirInfo & wd, bool export
         wd.files.empty()
         ? makeEmptySourceAccessor()
         : AllowListInputAccessor::create(
-            makeFSInputAccessor(path),
+            makeFSSourceAccessor(path),
             std::set<CanonPath> { wd.files },
             std::move(makeNotAllowedError)).cast<SourceAccessor>();
     if (exportIgnore)
diff --git a/src/libfetchers/path.cc b/src/libfetchers/path.cc
index 1e9683ae1..68958d559 100644
--- a/src/libfetchers/path.cc
+++ b/src/libfetchers/path.cc
@@ -1,8 +1,7 @@
 #include "fetchers.hh"
 #include "store-api.hh"
 #include "archive.hh"
-#include "fs-input-accessor.hh"
-#include "posix-source-accessor.hh"
+#include "store-path-accessor.hh"
 
 namespace nix::fetchers {
 
diff --git a/src/libfetchers/store-path-accessor.cc b/src/libfetchers/store-path-accessor.cc
new file mode 100644
index 000000000..6eeeba3e8
--- /dev/null
+++ b/src/libfetchers/store-path-accessor.cc
@@ -0,0 +1,17 @@
+#include "store-path-accessor.hh"
+#include "store-api.hh"
+
+namespace nix {
+
+ref<SourceAccessor> makeStorePathAccessor(
+    ref<Store> store,
+    const StorePath & storePath)
+{
+    // FIXME: should use `store->getFSAccessor()`
+    auto root = std::filesystem::path { store->toRealPath(storePath) };
+    auto accessor = makeFSSourceAccessor(root);
+    accessor->setPathDisplay(root.string());
+    return accessor;
+}
+
+}
diff --git a/src/libfetchers/fs-input-accessor.hh b/src/libfetchers/store-path-accessor.hh
similarity index 67%
rename from src/libfetchers/fs-input-accessor.hh
rename to src/libfetchers/store-path-accessor.hh
index 80dc74725..4aa55c4df 100644
--- a/src/libfetchers/fs-input-accessor.hh
+++ b/src/libfetchers/store-path-accessor.hh
@@ -7,10 +7,6 @@ namespace nix {
 class StorePath;
 class Store;
 
-ref<SourceAccessor> makeFSInputAccessor();
-
-ref<SourceAccessor> makeFSInputAccessor(std::filesystem::path root);
-
 ref<SourceAccessor> makeStorePathAccessor(
     ref<Store> store,
     const StorePath & storePath);
diff --git a/src/libfetchers/tarball.cc b/src/libfetchers/tarball.cc
index 8ebc2c296..33c8f3c0c 100644
--- a/src/libfetchers/tarball.cc
+++ b/src/libfetchers/tarball.cc
@@ -8,8 +8,7 @@
 #include "tarfile.hh"
 #include "types.hh"
 #include "split.hh"
-#include "posix-source-accessor.hh"
-#include "fs-input-accessor.hh"
+#include "store-path-accessor.hh"
 #include "store-api.hh"
 #include "git-utils.hh"
 
diff --git a/src/libfetchers/unix/git.cc b/src/libfetchers/unix/git.cc
index be44b2eda..c8fd295c0 100644
--- a/src/libfetchers/unix/git.cc
+++ b/src/libfetchers/unix/git.cc
@@ -9,7 +9,6 @@
 #include "pathlocks.hh"
 #include "processes.hh"
 #include "git.hh"
-#include "fs-input-accessor.hh"
 #include "mounted-input-accessor.hh"
 #include "git-utils.hh"
 #include "logging.hh"
diff --git a/src/libfetchers/unix/mercurial.cc b/src/libfetchers/unix/mercurial.cc
index e85f7e854..4d95f54f0 100644
--- a/src/libfetchers/unix/mercurial.cc
+++ b/src/libfetchers/unix/mercurial.cc
@@ -6,8 +6,7 @@
 #include "tarfile.hh"
 #include "store-api.hh"
 #include "url-parts.hh"
-#include "fs-input-accessor.hh"
-#include "posix-source-accessor.hh"
+#include "store-path-accessor.hh"
 #include "fetch-settings.hh"
 
 #include <sys/time.h>
@@ -211,10 +210,9 @@ struct MercurialInputScheme : InputScheme
                     return files.count(file);
                 };
 
-                PosixSourceAccessor accessor;
                 auto storePath = store->addToStore(
                     input.getName(),
-                    accessor, CanonPath { actualPath },
+                    *makeFSSourceAccessor(), CanonPath { actualPath },
                     FileIngestionMethod::Recursive, HashAlgorithm::SHA256, {},
                     filter);
 
@@ -320,8 +318,7 @@ struct MercurialInputScheme : InputScheme
 
         deletePath(tmpDir + "/.hg_archival.txt");
 
-        PosixSourceAccessor accessor;
-        auto storePath = store->addToStore(name, accessor, CanonPath { tmpDir });
+        auto storePath = store->addToStore(name, *makeFSSourceAccessor(), CanonPath { tmpDir });
 
         Attrs infoAttrs({
             {"rev", input.getRev()->gitRev()},
diff --git a/src/libutil/posix-source-accessor.cc b/src/libutil/posix-source-accessor.cc
index a589bfd3d..f7dffb871 100644
--- a/src/libutil/posix-source-accessor.cc
+++ b/src/libutil/posix-source-accessor.cc
@@ -166,4 +166,14 @@ void PosixSourceAccessor::assertNoSymlinks(CanonPath path)
     }
 }
 
+ref<SourceAccessor> makeFSSourceAccessor()
+{
+    static auto rootFS = make_ref<PosixSourceAccessor>();
+    return rootFS;
+}
+
+ref<SourceAccessor> makeFSSourceAccessor(std::filesystem::path root)
+{
+    return make_ref<PosixSourceAccessor>(std::move(root));
+}
 }
diff --git a/src/libutil/source-accessor.hh b/src/libutil/source-accessor.hh
index 5f1afb946..548feddfd 100644
--- a/src/libutil/source-accessor.hh
+++ b/src/libutil/source-accessor.hh
@@ -194,4 +194,14 @@ ref<SourceAccessor> makeEmptySourceAccessor();
  */
 MakeError(RestrictedPathError, Error);
 
+/**
+ * Return an accessor for the root filesystem.
+ */
+ref<SourceAccessor> makeFSSourceAccessor();
+
+/**
+ * Return an accessor for the filesystem rooted at `root`.
+ */
+ref<SourceAccessor> makeFSSourceAccessor(std::filesystem::path root);
+
 }
diff --git a/tests/unit/libexpr/primops.cc b/tests/unit/libexpr/primops.cc
index 10c250d74..5b5898237 100644
--- a/tests/unit/libexpr/primops.cc
+++ b/tests/unit/libexpr/primops.cc
@@ -2,6 +2,7 @@
 #include <gtest/gtest.h>
 
 #include "eval-settings.hh"
+#include "memory-source-accessor.hh"
 
 #include "tests/libexpr.hh"