diff --git a/src/sinks.mbt b/src/sinks.mbt
index 2d7090c..ebfdd7d 100644
--- a/src/sinks.mbt
+++ b/src/sinks.mbt
@@ -44,327 +44,6 @@ pub impl Sink for JsonConsoleSink with write(self, rec) {
   println(format_json(rec))
 }
 
-pub struct FileSink {
-  path : String
-  append : Ref[Bool]
-  default_append : Bool
-  handle : Ref[FileHandle?]
-  formatter : RecordFormatter
-  auto_flush : Ref[Bool]
-  default_auto_flush : Bool
-  rotation : Ref[FileRotation?]
-  default_rotation : FileRotation?
-  open_failures : Ref[Int]
-  write_failures : Ref[Int]
-  flush_failures : Ref[Int]
-  rotation_failures : Ref[Int]
-}
-
-pub type FileRotation = @utils.FileRotation
-
-pub type FileSinkState = @utils.FileSinkState
-
-pub type FileSinkPolicy = @utils.FileSinkPolicy
-
-pub fn file_rotation(max_bytes : Int, max_backups~ : Int = 1) -> FileRotation {
-  @utils.file_rotation(max_bytes, max_backups=max_backups)
-}
-
-pub fn native_files_supported() -> Bool {
-  native_files_supported_internal()
-}
-
-pub fn file_sink(
-  path : String,
-  append~ : Bool = true,
-  auto_flush~ : Bool = true,
-  rotation~ : FileRotation? = None,
-  formatter~ : RecordFormatter = fn(rec) {
-    format_text(rec)
-  },
-) -> FileSink {
-  let handle = open_file_handle_internal(path, append)
-  {
-    path,
-    append: Ref(append),
-    default_append: append,
-    handle: Ref(handle),
-    formatter,
-    auto_flush: Ref(auto_flush),
-    default_auto_flush: auto_flush,
-    rotation: Ref(rotation),
-    default_rotation: rotation,
-    open_failures: Ref(if handle is Some(_) { 0 } else { 1 }),
-    write_failures: Ref(0),
-    flush_failures: Ref(0),
-    rotation_failures: Ref(0),
-  }
-}
-
-pub fn FileSink::is_available(self : FileSink) -> Bool {
-  self.handle.val is Some(_)
-}
-
-pub fn FileSink::flush(self : FileSink) -> Bool {
-  match self.handle.val {
-    None => false
-    Some(handle) => {
-      let ok = flush_file_handle_internal(handle)
-      if !ok {
-        self.flush_failures.val += 1
-      }
-      ok
-    }
-  }
-}
-
-pub fn FileSink::append_mode(self : FileSink) -> Bool {
-  self.append.val
-}
-
-pub fn FileSink::set_append_mode(self : FileSink, append : Bool) -> Unit {
-  self.append.val = append
-}
-
-pub fn FileSink::path(self : FileSink) -> String {
-  self.path
-}
-
-pub fn FileSink::auto_flush_enabled(self : FileSink) -> Bool {
-  self.auto_flush.val
-}
-
-pub fn FileSink::rotation_enabled(self : FileSink) -> Bool {
-  self.rotation.val is Some(_)
-}
-
-pub fn FileSink::rotation_config(self : FileSink) -> FileRotation? {
-  self.rotation.val
-}
-
-pub fn FileSink::set_auto_flush(self : FileSink, enabled : Bool) -> Unit {
-  self.auto_flush.val = enabled
-}
-
-pub fn FileSink::set_policy(self : FileSink, policy : FileSinkPolicy) -> Unit {
-  self.append.val = policy.append
-  self.auto_flush.val = policy.auto_flush
-  self.rotation.val = policy.rotation
-}
-
-pub fn FileSink::set_rotation(self : FileSink, rotation : FileRotation?) -> Unit {
-  self.rotation.val = rotation
-}
-
-pub fn FileSink::clear_rotation(self : FileSink) -> Unit {
-  self.rotation.val = None
-}
-
-pub fn FileSink::close(self : FileSink) -> Bool {
-  match self.handle.val {
-    None => false
-    Some(handle) => {
-      let ok = close_file_handle_internal(handle)
-      self.handle.val = None
-      ok
-    }
-  }
-}
-
-pub fn FileSink::rotation_failures(self : FileSink) -> Int {
-  self.rotation_failures.val
-}
-
-pub fn FileSink::open_failures(self : FileSink) -> Int {
-  self.open_failures.val
-}
-
-pub fn FileSink::write_failures(self : FileSink) -> Int {
-  self.write_failures.val
-}
-
-pub fn FileSink::flush_failures(self : FileSink) -> Int {
-  self.flush_failures.val
-}
-
-pub fn FileSink::reset_failure_counters(self : FileSink) -> Unit {
-  self.open_failures.val = 0
-  self.write_failures.val = 0
-  self.flush_failures.val = 0
-  self.rotation_failures.val = 0
-}
-
-pub fn FileSink::reset_policy(self : FileSink) -> Unit {
-  self.append.val = self.default_append
-  self.auto_flush.val = self.default_auto_flush
-  self.rotation.val = self.default_rotation
-}
-
-pub fn FileSink::policy(self : FileSink) -> FileSinkPolicy {
-  FileSinkPolicy::new(
-    append=self.append.val,
-    auto_flush=self.auto_flush.val,
-    rotation=self.rotation.val,
-  )
-}
-
-pub fn FileSink::default_policy(self : FileSink) -> FileSinkPolicy {
-  FileSinkPolicy::new(
-    append=self.default_append,
-    auto_flush=self.default_auto_flush,
-    rotation=self.default_rotation,
-  )
-}
-
-pub fn FileSink::policy_matches_default(self : FileSink) -> Bool {
-  let current = self.policy()
-  let default = self.default_policy()
-  current.append == default.append &&
-  current.auto_flush == default.auto_flush &&
-  policy_rotation_equals_internal(current.rotation, default.rotation)
-}
-
-fn policy_rotation_equals_internal(left : FileRotation?, right : FileRotation?) -> Bool {
-  match (left, right) {
-    (None, None) => true
-    (Some(a), Some(b)) => a.max_bytes == b.max_bytes && a.max_backups == b.max_backups
-    _ => false
-  }
-}
-
-pub fn FileSink::state(self : FileSink) -> FileSinkState {
-  FileSinkState::new(
-    self.path,
-    available=self.is_available(),
-    append=self.append.val,
-    auto_flush=self.auto_flush.val,
-    rotation=self.rotation.val,
-    open_failures=self.open_failures.val,
-    write_failures=self.write_failures.val,
-    flush_failures=self.flush_failures.val,
-    rotation_failures=self.rotation_failures.val,
-  )
-}
-
-pub fn FileSink::reopen(self : FileSink, append~ : Bool? = None) -> Bool {
-  let append_mode = append.unwrap_or(self.append.val)
-  self.append.val = append_mode
-  match self.handle.val {
-    None => ()
-    Some(handle) => {
-      ignore(close_file_handle_internal(handle))
-      self.handle.val = None
-    }
-  }
-  let reopened = open_file_handle_internal(self.path, append_mode)
-  self.handle.val = reopened
-  if reopened is Some(_) {
-    true
-  } else {
-    self.open_failures.val += 1
-    false
-  }
-}
-
-pub fn FileSink::reopen_with_current_policy(self : FileSink) -> Bool {
-  self.reopen()
-}
-
-pub fn FileSink::reopen_append(self : FileSink) -> Bool {
-  self.reopen(append=Some(true))
-}
-
-pub fn FileSink::reopen_truncate(self : FileSink) -> Bool {
-  self.reopen(append=Some(false))
-}
-
-fn rotated_file_path(path : String, index : Int) -> String {
-  "\{path}.\{index}"
-}
-
-fn rotate_file_sink_internal(sink : FileSink, rotation : FileRotation) -> Bool {
-  let closed = match sink.handle.val {
-    None => true
-    Some(handle) => {
-      let ok = close_file_handle_internal(handle)
-      sink.handle.val = None
-      ok
-    }
-  }
-  if !closed {
-    return false
-  }
-  if rotation.max_backups > 0 {
-    ignore(remove_file_internal(rotated_file_path(sink.path, rotation.max_backups)))
-    for index = rotation.max_backups - 1; index >= 1; {
-      let from_path = rotated_file_path(sink.path, index)
-      let to_path = rotated_file_path(sink.path, index + 1)
-      ignore(rename_file_internal(from_path, to_path))
-      continue index - 1
-    }
-    ignore(rename_file_internal(sink.path, rotated_file_path(sink.path, 1)))
-  } else {
-    ignore(remove_file_internal(sink.path))
-  }
-  sink.handle.val = open_file_handle_internal(sink.path, false)
-  sink.handle.val is Some(_)
-}
-
-fn rotate_if_needed_internal(sink : FileSink, next_line_bytes : Int) -> Bool {
-  match sink.rotation.val {
-    None => true
-    Some(rotation) => match sink.handle.val {
-      None => false
-      Some(handle) => {
-        let size = file_size_internal(handle)
-        if size + next_line_bytes <= rotation.max_bytes {
-          true
-        } else {
-          let rotated = rotate_file_sink_internal(sink, rotation)
-          if !rotated {
-            sink.rotation_failures.val += 1
-          }
-          rotated
-        }
-      }
-    }
-  }
-}
-
-pub impl Sink for FileSink with write(self, rec) {
-  match self.handle.val {
-    None => {
-      self.write_failures.val += 1
-    }
-    Some(_) => {
-      let line = "\{(self.formatter)(rec)}\n"
-      let can_write = rotate_if_needed_internal(self, string_byte_length_internal(line))
-      if can_write {
-        match self.handle.val {
-          None => {
-            self.write_failures.val += 1
-          }
-          Some(active) => {
-            let wrote = write_file_handle_internal(active, line)
-            if wrote {
-              if self.auto_flush.val {
-                let flushed = flush_file_handle_internal(active)
-                if !flushed {
-                  self.flush_failures.val += 1
-                }
-              }
-            } else {
-              self.write_failures.val += 1
-            }
-          }
-        }
-      } else {
-        self.write_failures.val += 1
-      }
-    }
-  }
-}
-
 pub struct FormattedConsoleSink {
   formatter : RecordFormatter
 }
diff --git a/src/sinks_file.mbt b/src/sinks_file.mbt
new file mode 100644
index 0000000..de4cbbb
--- /dev/null
+++ b/src/sinks_file.mbt
@@ -0,0 +1,320 @@
+pub struct FileSink {
+  path : String
+  append : Ref[Bool]
+  default_append : Bool
+  handle : Ref[FileHandle?]
+  formatter : RecordFormatter
+  auto_flush : Ref[Bool]
+  default_auto_flush : Bool
+  rotation : Ref[FileRotation?]
+  default_rotation : FileRotation?
+  open_failures : Ref[Int]
+  write_failures : Ref[Int]
+  flush_failures : Ref[Int]
+  rotation_failures : Ref[Int]
+}
+
+pub type FileRotation = @utils.FileRotation
+
+pub type FileSinkState = @utils.FileSinkState
+
+pub type FileSinkPolicy = @utils.FileSinkPolicy
+
+pub fn file_rotation(max_bytes : Int, max_backups~ : Int = 1) -> FileRotation {
+  @utils.file_rotation(max_bytes, max_backups=max_backups)
+}
+
+pub fn native_files_supported() -> Bool {
+  native_files_supported_internal()
+}
+
+pub fn file_sink(
+  path : String,
+  append~ : Bool = true,
+  auto_flush~ : Bool = true,
+  rotation~ : FileRotation? = None,
+  formatter~ : RecordFormatter = fn(rec) {
+    format_text(rec)
+  },
+) -> FileSink {
+  let handle = open_file_handle_internal(path, append)
+  {
+    path,
+    append: Ref(append),
+    default_append: append,
+    handle: Ref(handle),
+    formatter,
+    auto_flush: Ref(auto_flush),
+    default_auto_flush: auto_flush,
+    rotation: Ref(rotation),
+    default_rotation: rotation,
+    open_failures: Ref(if handle is Some(_) { 0 } else { 1 }),
+    write_failures: Ref(0),
+    flush_failures: Ref(0),
+    rotation_failures: Ref(0),
+  }
+}
+
+pub fn FileSink::is_available(self : FileSink) -> Bool {
+  self.handle.val is Some(_)
+}
+
+pub fn FileSink::flush(self : FileSink) -> Bool {
+  match self.handle.val {
+    None => false
+    Some(handle) => {
+      let ok = flush_file_handle_internal(handle)
+      if !ok {
+        self.flush_failures.val += 1
+      }
+      ok
+    }
+  }
+}
+
+pub fn FileSink::append_mode(self : FileSink) -> Bool {
+  self.append.val
+}
+
+pub fn FileSink::set_append_mode(self : FileSink, append : Bool) -> Unit {
+  self.append.val = append
+}
+
+pub fn FileSink::path(self : FileSink) -> String {
+  self.path
+}
+
+pub fn FileSink::auto_flush_enabled(self : FileSink) -> Bool {
+  self.auto_flush.val
+}
+
+pub fn FileSink::rotation_enabled(self : FileSink) -> Bool {
+  self.rotation.val is Some(_)
+}
+
+pub fn FileSink::rotation_config(self : FileSink) -> FileRotation? {
+  self.rotation.val
+}
+
+pub fn FileSink::set_auto_flush(self : FileSink, enabled : Bool) -> Unit {
+  self.auto_flush.val = enabled
+}
+
+pub fn FileSink::set_policy(self : FileSink, policy : FileSinkPolicy) -> Unit {
+  self.append.val = policy.append
+  self.auto_flush.val = policy.auto_flush
+  self.rotation.val = policy.rotation
+}
+
+pub fn FileSink::set_rotation(self : FileSink, rotation : FileRotation?) -> Unit {
+  self.rotation.val = rotation
+}
+
+pub fn FileSink::clear_rotation(self : FileSink) -> Unit {
+  self.rotation.val = None
+}
+
+pub fn FileSink::close(self : FileSink) -> Bool {
+  match self.handle.val {
+    None => false
+    Some(handle) => {
+      let ok = close_file_handle_internal(handle)
+      self.handle.val = None
+      ok
+    }
+  }
+}
+
+pub fn FileSink::rotation_failures(self : FileSink) -> Int {
+  self.rotation_failures.val
+}
+
+pub fn FileSink::open_failures(self : FileSink) -> Int {
+  self.open_failures.val
+}
+
+pub fn FileSink::write_failures(self : FileSink) -> Int {
+  self.write_failures.val
+}
+
+pub fn FileSink::flush_failures(self : FileSink) -> Int {
+  self.flush_failures.val
+}
+
+pub fn FileSink::reset_failure_counters(self : FileSink) -> Unit {
+  self.open_failures.val = 0
+  self.write_failures.val = 0
+  self.flush_failures.val = 0
+  self.rotation_failures.val = 0
+}
+
+pub fn FileSink::reset_policy(self : FileSink) -> Unit {
+  self.append.val = self.default_append
+  self.auto_flush.val = self.default_auto_flush
+  self.rotation.val = self.default_rotation
+}
+
+pub fn FileSink::policy(self : FileSink) -> FileSinkPolicy {
+  FileSinkPolicy::new(
+    append=self.append.val,
+    auto_flush=self.auto_flush.val,
+    rotation=self.rotation.val,
+  )
+}
+
+pub fn FileSink::default_policy(self : FileSink) -> FileSinkPolicy {
+  FileSinkPolicy::new(
+    append=self.default_append,
+    auto_flush=self.default_auto_flush,
+    rotation=self.default_rotation,
+  )
+}
+
+pub fn FileSink::policy_matches_default(self : FileSink) -> Bool {
+  let current = self.policy()
+  let default = self.default_policy()
+  current.append == default.append &&
+  current.auto_flush == default.auto_flush &&
+  policy_rotation_equals_internal(current.rotation, default.rotation)
+}
+
+fn policy_rotation_equals_internal(left : FileRotation?, right : FileRotation?) -> Bool {
+  match (left, right) {
+    (None, None) => true
+    (Some(a), Some(b)) => a.max_bytes == b.max_bytes && a.max_backups == b.max_backups
+    _ => false
+  }
+}
+
+pub fn FileSink::state(self : FileSink) -> FileSinkState {
+  FileSinkState::new(
+    self.path,
+    available=self.is_available(),
+    append=self.append.val,
+    auto_flush=self.auto_flush.val,
+    rotation=self.rotation.val,
+    open_failures=self.open_failures.val,
+    write_failures=self.write_failures.val,
+    flush_failures=self.flush_failures.val,
+    rotation_failures=self.rotation_failures.val,
+  )
+}
+
+pub fn FileSink::reopen(self : FileSink, append~ : Bool? = None) -> Bool {
+  let append_mode = append.unwrap_or(self.append.val)
+  self.append.val = append_mode
+  match self.handle.val {
+    None => ()
+    Some(handle) => {
+      ignore(close_file_handle_internal(handle))
+      self.handle.val = None
+    }
+  }
+  let reopened = open_file_handle_internal(self.path, append_mode)
+  self.handle.val = reopened
+  if reopened is Some(_) {
+    true
+  } else {
+    self.open_failures.val += 1
+    false
+  }
+}
+
+pub fn FileSink::reopen_with_current_policy(self : FileSink) -> Bool {
+  self.reopen()
+}
+
+pub fn FileSink::reopen_append(self : FileSink) -> Bool {
+  self.reopen(append=Some(true))
+}
+
+pub fn FileSink::reopen_truncate(self : FileSink) -> Bool {
+  self.reopen(append=Some(false))
+}
+
+fn rotated_file_path(path : String, index : Int) -> String {
+  "\{path}.\{index}"
+}
+
+fn rotate_file_sink_internal(sink : FileSink, rotation : FileRotation) -> Bool {
+  let closed = match sink.handle.val {
+    None => true
+    Some(handle) => {
+      let ok = close_file_handle_internal(handle)
+      sink.handle.val = None
+      ok
+    }
+  }
+  if !closed {
+    return false
+  }
+  if rotation.max_backups > 0 {
+    ignore(remove_file_internal(rotated_file_path(sink.path, rotation.max_backups)))
+    for index = rotation.max_backups - 1; index >= 1; {
+      let from_path = rotated_file_path(sink.path, index)
+      let to_path = rotated_file_path(sink.path, index + 1)
+      ignore(rename_file_internal(from_path, to_path))
+      continue index - 1
+    }
+    ignore(rename_file_internal(sink.path, rotated_file_path(sink.path, 1)))
+  } else {
+    ignore(remove_file_internal(sink.path))
+  }
+  sink.handle.val = open_file_handle_internal(sink.path, false)
+  sink.handle.val is Some(_)
+}
+
+fn rotate_if_needed_internal(sink : FileSink, next_line_bytes : Int) -> Bool {
+  match sink.rotation.val {
+    None => true
+    Some(rotation) => match sink.handle.val {
+      None => false
+      Some(handle) => {
+        let size = file_size_internal(handle)
+        if size + next_line_bytes <= rotation.max_bytes {
+          true
+        } else {
+          let rotated = rotate_file_sink_internal(sink, rotation)
+          if !rotated {
+            sink.rotation_failures.val += 1
+          }
+          rotated
+        }
+      }
+    }
+  }
+}
+
+pub impl Sink for FileSink with write(self, rec) {
+  match self.handle.val {
+    None => {
+      self.write_failures.val += 1
+    }
+    Some(_) => {
+      let line = "\{(self.formatter)(rec)}\n"
+      let can_write = rotate_if_needed_internal(self, string_byte_length_internal(line))
+      if can_write {
+        match self.handle.val {
+          None => {
+            self.write_failures.val += 1
+          }
+          Some(active) => {
+            let wrote = write_file_handle_internal(active, line)
+            if wrote {
+              if self.auto_flush.val {
+                let flushed = flush_file_handle_internal(active)
+                if !flushed {
+                  self.flush_failures.val += 1
+                }
+              }
+            } else {
+              self.write_failures.val += 1
+            }
+          }
+        }
+      } else {
+        self.write_failures.val += 1
+      }
+    }
+  }
+}