diff --git a/src/core/file.cc b/src/core/file.cc
index 1a05f819cf7..f2088404fb9 100644
--- a/src/core/file.cc
+++ b/src/core/file.cc
@@ -1078,7 +1078,8 @@ make_file_impl(int fd, file_open_options options, int flags, struct stat st) noe
     auto st_dev = st.st_dev;
     static thread_local std::unordered_map<decltype(st_dev), internal::fs_info> s_fstype;
 
-    if (s_fstype.count(st_dev) == 0) {
+    auto i = s_fstype.find(st_dev);
+    if (i == s_fstype.end()) [[unlikely]] {
         return engine().fstatfs(fd).then([fd, options = std::move(options), flags, st = std::move(st)] (struct statfs sfs) {
             internal::fs_info fsi;
             fsi.block_size = sfs.f_bsize;
@@ -1126,13 +1127,12 @@ make_file_impl(int fd, file_open_options options, int flags, struct stat st) noe
                 fsi.fsync_is_exclusive = true;
                 fsi.nowait_works = false;
             }
-            auto st_dev = st.st_dev;
-            s_fstype[st_dev] = std::move(fsi);
+            s_fstype.insert(std::make_pair(st.st_dev, std::move(fsi)));
             return make_file_impl(fd, std::move(options), flags, std::move(st));
         });
     }
 
-    const internal::fs_info& fsi = s_fstype[st_dev];
+    const internal::fs_info& fsi = i->second;
     if (!fsi.append_challenged || options.append_is_unlikely || ((flags & O_ACCMODE) == O_RDONLY)) {
         return make_ready_future<shared_ptr<file_impl>>(make_shared<posix_file_real_impl>(fd, open_flags(flags), std::move(options), fsi, st_dev));
     }