diff --git a/components/fatfs/src/vfs_fat.c b/components/fatfs/src/vfs_fat.c
index df2eb4cadf..9b33bd20e6 100644
--- a/components/fatfs/src/vfs_fat.c
+++ b/components/fatfs/src/vfs_fat.c
@@ -45,7 +45,7 @@ typedef struct {
 
 static const char* TAG = "vfs_fat";
 
-static size_t vfs_fat_write(void* p, int fd, const void * data, size_t size);
+static ssize_t vfs_fat_write(void* p, int fd, const void * data, size_t size);
 static off_t vfs_fat_lseek(void* p, int fd, off_t size, int mode);
 static ssize_t vfs_fat_read(void* ctx, int fd, void * dst, size_t size);
 static int vfs_fat_open(void* ctx, const char * path, int flags, int mode);
@@ -290,7 +290,7 @@ out:
     return fd;
 }
 
-static size_t vfs_fat_write(void* ctx, int fd, const void * data, size_t size)
+static ssize_t vfs_fat_write(void* ctx, int fd, const void * data, size_t size)
 {
     vfs_fat_ctx_t* fat_ctx = (vfs_fat_ctx_t*) ctx;
     FIL* file = &fat_ctx->files[fd];
diff --git a/components/vfs/README.rst b/components/vfs/README.rst
index 318004c250..ebd30ba0b1 100644
--- a/components/vfs/README.rst
+++ b/components/vfs/README.rst
@@ -37,7 +37,7 @@ Depending on the way FS driver declares its APIs, either ``read``, ``write``, et
 
 Case 1: API functions are declared without an extra context pointer (FS driver is a singleton)::
 
-    size_t myfs_write(int fd, const void * data, size_t size);
+    ssize_t myfs_write(int fd, const void * data, size_t size);
 
     // In definition of esp_vfs_t:
         .flags = ESP_VFS_FLAG_DEFAULT,
@@ -49,7 +49,7 @@ Case 1: API functions are declared without an extra context pointer (FS driver i
 
 Case 2: API functions are declared with an extra context pointer (FS driver supports multiple instances)::
 
-    size_t myfs_write(myfs_t* fs, int fd, const void * data, size_t size);
+    ssize_t myfs_write(myfs_t* fs, int fd, const void * data, size_t size);
 
     // In definition of esp_vfs_t:
         .flags = ESP_VFS_FLAG_CONTEXT_PTR,
diff --git a/components/vfs/include/esp_vfs.h b/components/vfs/include/esp_vfs.h
index 304750aabd..a3ce6b95cf 100644
--- a/components/vfs/include/esp_vfs.h
+++ b/components/vfs/include/esp_vfs.h
@@ -69,8 +69,8 @@ typedef struct
     int fd_offset;  /*!< file descriptor offset, determined by the FS driver */
     int flags;      /*!< ESP_VFS_FLAG_CONTEXT_PTR or ESP_VFS_FLAG_DEFAULT */
     union {
-        size_t (*write_p)(void* p, int fd, const void * data, size_t size);
-        size_t (*write)(int fd, const void * data, size_t size);
+        ssize_t (*write_p)(void* p, int fd, const void * data, size_t size);
+        ssize_t (*write)(int fd, const void * data, size_t size);
     };
     union {
         off_t (*lseek_p)(void* p, int fd, off_t size, int mode);
diff --git a/components/vfs/vfs.c b/components/vfs/vfs.c
index fff3a93a1d..565edd3659 100644
--- a/components/vfs/vfs.c
+++ b/components/vfs/vfs.c
@@ -213,7 +213,7 @@ ssize_t esp_vfs_write(struct _reent *r, int fd, const void * data, size_t size)
         return -1;
     }
     int local_fd = translate_fd(vfs, fd);
-    int ret;
+    ssize_t ret;
     CHECK_AND_CALL(ret, r, vfs, write, local_fd, data, size);
     return ret;
 }
@@ -226,7 +226,7 @@ off_t esp_vfs_lseek(struct _reent *r, int fd, off_t size, int mode)
         return -1;
     }
     int local_fd = translate_fd(vfs, fd);
-    int ret;
+    off_t ret;
     CHECK_AND_CALL(ret, r, vfs, lseek, local_fd, size, mode);
     return ret;
 }
@@ -239,7 +239,7 @@ ssize_t esp_vfs_read(struct _reent *r, int fd, void * dst, size_t size)
         return -1;
     }
     int local_fd = translate_fd(vfs, fd);
-    int ret;
+    ssize_t ret;
     CHECK_AND_CALL(ret, r, vfs, read, local_fd, dst, size);
     return ret;
 }
diff --git a/components/vfs/vfs_uart.c b/components/vfs/vfs_uart.c
index 545a5474fa..4b37487649 100644
--- a/components/vfs/vfs_uart.c
+++ b/components/vfs/vfs_uart.c
@@ -47,7 +47,7 @@ static void IRAM_ATTR uart_tx_char(uart_dev_t* uart, int c)
 }
 
 
-static size_t IRAM_ATTR uart_write(int fd, const void * data, size_t size)
+static ssize_t IRAM_ATTR uart_write(int fd, const void * data, size_t size)
 {
     assert(fd >=0 && fd < 3);
     const char *data_c = (const char *)data;