diff --git a/src/writerthread.cpp b/src/writerthread.cpp
index 5d21091a..759d5cc9 100644
--- a/src/writerthread.cpp
+++ b/src/writerthread.cpp
@@ -14,7 +14,8 @@ WriterThread::WriterThread(Options* opt, string filename, bool isSTDOUT){
     mInputCompleted = false;
     mFilename = filename;
 
-    mPwriteMode = !isSTDOUT && ends_with(filename, ".gz") && mOptions->thread > 1;
+    mGzipMode = ends_with(filename, ".gz");
+    mPwriteMode = !isSTDOUT && mOptions->thread > 1;
     mFd = -1;
     mOffsetRing = NULL;
     mNextSeq = NULL;
@@ -31,15 +32,17 @@ WriterThread::WriterThread(Options* opt, string filename, bool isSTDOUT){
         mNextSeq = new size_t[mOptions->thread];
         for (int t = 0; t < mOptions->thread; t++)
             mNextSeq[t] = t;
-        mCompressors = new libdeflate_compressor*[mOptions->thread];
-        for (int t = 0; t < mOptions->thread; t++)
-            mCompressors[t] = libdeflate_alloc_compressor(mOptions->compression);
-        size_t initBufSize = PACK_SIZE * 500;
-        mCompBufs = new char*[mOptions->thread];
-        mCompBufSizes = new size_t[mOptions->thread];
-        for (int t = 0; t < mOptions->thread; t++) {
-            mCompBufs[t] = new char[initBufSize];
-            mCompBufSizes[t] = initBufSize;
+        if (mGzipMode) {
+            mCompressors = new libdeflate_compressor*[mOptions->thread];
+            for (int t = 0; t < mOptions->thread; t++)
+                mCompressors[t] = libdeflate_alloc_compressor(mOptions->compression);
+            size_t initBufSize = PACK_SIZE * 500;
+            mCompBufs = new char*[mOptions->thread];
+            mCompBufSizes = new size_t[mOptions->thread];
+            for (int t = 0; t < mOptions->thread; t++) {
+                mCompBufs[t] = new char[initBufSize];
+                mCompBufSizes[t] = initBufSize;
+            }
         }
         mWorkingBufferList = 0;
         mBufferLength = 0;
@@ -116,20 +119,22 @@ void WriterThread::input(int tid, string* data) {
 }
 
 void WriterThread::inputPwrite(int tid, string* data) {
-    size_t bound = libdeflate_gzip_compress_bound(mCompressors[tid], data->size());
-    // Grow per-worker buffer if needed
-    if (bound > mCompBufSizes[tid]) {
-        delete[] mCompBufs[tid];
-        mCompBufs[tid] = new char[bound];
-        mCompBufSizes[tid] = bound;
+    const char* writeData = data->data();
+    size_t wsize = data->size();
+    if (mGzipMode) {
+        size_t bound = libdeflate_gzip_compress_bound(mCompressors[tid], data->size());
+        if (bound > mCompBufSizes[tid]) {
+            delete[] mCompBufs[tid];
+            mCompBufs[tid] = new char[bound];
+            mCompBufSizes[tid] = bound;
+        }
+        size_t outsize = libdeflate_gzip_compress(mCompressors[tid], data->data(), data->size(),
+                                                   mCompBufs[tid], bound);
+        if (outsize == 0)
+            error_exit("libdeflate gzip compression failed");
+        writeData = mCompBufs[tid];
+        wsize = outsize;
     }
-    size_t outsize = libdeflate_gzip_compress(mCompressors[tid], data->data(), data->size(),
-                                               mCompBufs[tid], bound);
-    if (outsize == 0)
-        error_exit("libdeflate gzip compression failed");
-    delete data;
-    const char* writeData = mCompBufs[tid];
-    size_t wsize = outsize;
 
     size_t seq = mNextSeq[tid];
 
@@ -163,6 +168,7 @@ void WriterThread::inputPwrite(int tid, string* data) {
             written += ret;
         }
     }
+    delete data;
 
     mNextSeq[tid] += mOptions->thread;
 }
diff --git a/src/writerthread.h b/src/writerthread.h
index 053d27f6..9da5e031 100644
--- a/src/writerthread.h
+++ b/src/writerthread.h
@@ -55,14 +55,14 @@ class WriterThread{
     SingleProducerSingleConsumerList<string*>** mBufferLists;
     int mWorkingBufferList;
 
-    // pwrite mode: parallel libdeflate gz compression + direct file write
     bool mPwriteMode;
+    bool mGzipMode;
     int mFd;
     OffsetSlot* mOffsetRing;
     size_t* mNextSeq;
     libdeflate_compressor** mCompressors;
-    char** mCompBufs;       // per-worker pre-allocated compress output buffers
-    size_t* mCompBufSizes;  // per-worker buffer sizes
+    char** mCompBufs;
+    size_t* mCompBufSizes;
 };
 
 #endif