diff --git a/libraries/AP_Logger/AP_Logger_File.cpp b/libraries/AP_Logger/AP_Logger_File.cpp
index c379e5e6ad..e38ed3b304 100644
--- a/libraries/AP_Logger/AP_Logger_File.cpp
+++ b/libraries/AP_Logger/AP_Logger_File.cpp
@@ -29,10 +29,6 @@ extern const AP_HAL::HAL& hal;
 
 #define LOGGER_PAGE_SIZE 1024UL
 
-#ifndef HAL_LOGGER_WRITE_CHUNK_SIZE
-#define HAL_LOGGER_WRITE_CHUNK_SIZE 4096
-#endif
-
 #define MB_to_B 1000000
 #define B_to_MB 0.000001
 
@@ -46,11 +42,7 @@ AP_Logger_File::AP_Logger_File(AP_Logger &front,
                                LoggerMessageWriter_DFLogStart *writer,
                                const char *log_directory) :
     AP_Logger_Backend(front, writer),
-    _write_fd(-1),
-    _read_fd(-1),
-    _log_directory(log_directory),
-    _writebuf(0),
-    _writebuf_chunk(HAL_LOGGER_WRITE_CHUNK_SIZE)
+    _log_directory(log_directory)
 {
     df_stats_clear();
 }
diff --git a/libraries/AP_Logger/AP_Logger_File.h b/libraries/AP_Logger/AP_Logger_File.h
index a16cf77ede..7c0696b082 100644
--- a/libraries/AP_Logger/AP_Logger_File.h
+++ b/libraries/AP_Logger/AP_Logger_File.h
@@ -13,6 +13,10 @@
 #include <AP_HAL/utility/RingBuffer.h>
 #include "AP_Logger_Backend.h"
 
+#ifndef HAL_LOGGER_WRITE_CHUNK_SIZE
+#define HAL_LOGGER_WRITE_CHUNK_SIZE 4096
+#endif
+
 class AP_Logger_File : public AP_Logger_Backend
 {
 public:
@@ -59,14 +63,14 @@ protected:
     bool StartNewLogOK() const override;
 
 private:
-    int _write_fd;
+    int _write_fd = -1;
     char *_write_filename;
     uint32_t _last_write_ms;
 #if CONFIG_HAL_BOARD == HAL_BOARD_CHIBIOS
     bool _need_rtc_update;
 #endif
     
-    int _read_fd;
+    int _read_fd = -1;
     uint16_t _read_fd_log_num;
     uint32_t _read_offset;
     uint32_t _write_offset;
@@ -92,8 +96,8 @@ private:
     bool log_exists(const uint16_t lognum) const;
 
     // write buffer
-    ByteBuffer _writebuf;
-    const uint16_t _writebuf_chunk;
+    ByteBuffer _writebuf{0};
+    const uint16_t _writebuf_chunk = HAL_LOGGER_WRITE_CHUNK_SIZE;
     uint32_t _last_write_time;
 
     /* construct a file name given a log number. Caller must free. */