diff --git a/src/libutil/posix-source-accessor.cc b/src/libutil/posix-source-accessor.cc
index c524f3e4f..fe3bcb1c1 100644
--- a/src/libutil/posix-source-accessor.cc
+++ b/src/libutil/posix-source-accessor.cc
@@ -114,6 +114,8 @@ std::optional<SourceAccessor::Stat> PosixSourceAccessor::maybeLstat(const CanonP
     auto st = cachedLstat(path);
     if (!st)
         return std::nullopt;
+    // This makes the accessor thread-unsafe, but we only seem to use the actual value in a single threaded context in
+    // `src/libfetchers/path.cc`.
     mtime = std::max(mtime, st->st_mtime);
     return Stat{
         .type = S_ISREG(st->st_mode)   ? tRegular