diff --git a/src/libutil/file-system.cc b/src/libutil/file-system.cc
index a47df1692313..5ce8e98cd110 100644
--- a/src/libutil/file-system.cc
+++ b/src/libutil/file-system.cc
@@ -252,21 +252,15 @@ Path readLink(const Path & path)
 
 std::string readFile(const Path & path)
 {
-    AutoCloseFD fd = toDescriptor(open(
-        path.c_str(),
-        O_RDONLY
-#ifdef O_CLOEXEC
-            | O_CLOEXEC
-#endif
-        ));
-    if (!fd)
-        throw SysError("opening file '%1%'", path);
-    return readFile(fd.get());
+    return readFile(std::filesystem::path(path));
 }
 
 std::string readFile(const std::filesystem::path & path)
 {
-    return readFile(os_string_to_string(PathViewNG{path}));
+    AutoCloseFD fd = openFileReadonly(path);
+    if (!fd)
+        throw NativeSysError("opening file %1%", path);
+    return readFile(fd.get());
 }
 
 void readFile(const Path & path, Sink & sink, bool memory_map)
@@ -285,15 +279,9 @@ void readFile(const Path & path, Sink & sink, bool memory_map)
     }
 
     // Stream the file instead if memory-mapping fails or is disabled.
-    AutoCloseFD fd = toDescriptor(open(
-        path.c_str(),
-        O_RDONLY
-#ifdef O_CLOEXEC
-            | O_CLOEXEC
-#endif
-        ));
+    AutoCloseFD fd = openFileReadonly(std::filesystem::path(path));
     if (!fd)
-        throw SysError("opening file '%s'", path);
+        throw NativeSysError("opening file %s", path);
     drainFD(fd.get(), sink);
 }
 
diff --git a/src/libutil/nar-accessor.cc b/src/libutil/nar-accessor.cc
index 7387007e63b1..4cc956bbb9b5 100644
--- a/src/libutil/nar-accessor.cc
+++ b/src/libutil/nar-accessor.cc
@@ -268,7 +268,7 @@ GetNarBytes seekableGetNarBytes(const std::filesystem::path & path)
 {
     AutoCloseFD fd = openFileReadonly(path);
     if (!fd)
-        throw NativeSysError("opening NAR cache file '%s'", path);
+        throw NativeSysError("opening NAR cache file %s", path);
 
     return [inner = seekableGetNarBytes(fd.get()), fd = make_ref<AutoCloseFD>(std::move(fd))](
                uint64_t offset, uint64_t length) { return inner(offset, length); };
diff --git a/src/nix/cat.cc b/src/nix/cat.cc
index dcf47f1fa2bf..5b2a309a6ef7 100644
--- a/src/nix/cat.cc
+++ b/src/nix/cat.cc
@@ -52,7 +52,7 @@ struct CmdCatStore : StoreCommand, MixCat
 
 struct CmdCatNar : StoreCommand, MixCat
 {
-    Path narPath;
+    std::filesystem::path narPath;
 
     std::string path;
 
@@ -76,9 +76,9 @@ struct CmdCatNar : StoreCommand, MixCat
 
     void run(ref<Store> store) override
     {
-        AutoCloseFD fd = toDescriptor(open(narPath.c_str(), O_RDONLY));
+        AutoCloseFD fd = openFileReadonly(narPath);
         if (!fd)
-            throw SysError("opening NAR file '%s'", narPath);
+            throw NativeSysError("opening NAR file %s", narPath);
         auto source = FdSource{fd.get()};
 
         struct CatRegularFileSink : NullFileSystemObjectSink
diff --git a/src/nix/ls.cc b/src/nix/ls.cc
index 66f52a18afc0..9918132a6fff 100644
--- a/src/nix/ls.cc
+++ b/src/nix/ls.cc
@@ -126,7 +126,7 @@ struct CmdLsStore : StoreCommand, MixLs
 
 struct CmdLsNar : Command, MixLs
 {
-    Path narPath;
+    std::filesystem::path narPath;
 
     std::string path;
 
@@ -150,9 +150,9 @@ struct CmdLsNar : Command, MixLs
 
     void run() override
     {
-        AutoCloseFD fd = toDescriptor(open(narPath.c_str(), O_RDONLY));
+        AutoCloseFD fd = openFileReadonly(narPath);
         if (!fd)
-            throw SysError("opening NAR file '%s'", narPath);
+            throw NativeSysError("opening NAR file %s", narPath);
         auto source = FdSource{fd.get()};
         list(makeLazyNarAccessor(source, seekableGetNarBytes(fd.get())), CanonPath{path});
     }