diff --git a/ChangeLog.md b/ChangeLog.md
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -1,3 +1,7 @@
+## 2.4.7
+
+* Fixing interleaved log output when messages are larger than buffer size. [#103](https://github.com/kazu-yamamoto/logger/pull/103)
+
 ## 2.4.6
 
 * Ensuring that stdio is flushed. [#92](https://github.com/kazu-yamamoto/logger/pull/92)
diff --git a/System/Log/FastLogger/File.hs b/System/Log/FastLogger/File.hs
--- a/System/Log/FastLogger/File.hs
+++ b/System/Log/FastLogger/File.hs
@@ -9,8 +9,8 @@
 -- | The spec for logging files
 data FileLogSpec = FileLogSpec {
     log_file :: FilePath
-  , log_file_size :: Integer
-  , log_backup_number :: Int
+  , log_file_size :: Integer -- ^ Max log file size (in bytes) before requiring rotation.
+  , log_backup_number :: Int -- ^ Max number of rotated log files to keep around before overwriting the oldest one.
   }
 
 -- | Checking if a log file can be written.
diff --git a/System/Log/FastLogger/Logger.hs b/System/Log/FastLogger/Logger.hs
--- a/System/Log/FastLogger/Logger.hs
+++ b/System/Log/FastLogger/Logger.hs
@@ -10,6 +10,7 @@
 
 import Control.Concurrent (MVar, newMVar, withMVar)
 import Control.Monad (when)
+import Foreign.Marshal.Alloc (allocaBytes)
 import Foreign.Ptr (plusPtr)
 import System.Log.FastLogger.FileIO
 import System.Log.FastLogger.IO
@@ -35,7 +36,13 @@
 pushLog fd logger@(Logger mbuf size ref) nlogmsg@(LogStr nlen nbuilder)
   | nlen > size = do
       flushLog fd logger
-      withMVar mbuf $ \buf -> toBufIOWith buf size (write fd) nbuilder
+
+      -- Make sure we have a large enough buffer to hold the entire
+      -- contents, thereby allowing for a single write system call and
+      -- avoiding interleaving. This does not address the possibility
+      -- of write not writing the entire buffer at once.
+      allocaBytes nlen $ \buf -> withMVar mbuf $ \_ ->
+        toBufIOWith buf nlen (write fd) nbuilder
   | otherwise = do
     mmsg <- atomicModifyIORef' ref checkBuf
     case mmsg of
diff --git a/fast-logger.cabal b/fast-logger.cabal
--- a/fast-logger.cabal
+++ b/fast-logger.cabal
@@ -1,11 +1,12 @@
 Name:                   fast-logger
-Version:                2.4.6
+Version:                2.4.7
 Author:                 Kazu Yamamoto <kazu@iij.ad.jp>
 Maintainer:             Kazu Yamamoto <kazu@iij.ad.jp>
 License:                BSD3
 License-File:           LICENSE
 Synopsis:               A fast logging system
 Description:            A fast logging system
+Homepage:               https://github.com/kazu-yamamoto/logger
 Category:               System
 Cabal-Version:          >= 1.8
 Build-Type:             Simple