diff --git a/SPIFlash.cpp b/SPIFlash.cpp
index a0538da..20d1960 100644
--- a/SPIFlash.cpp
+++ b/SPIFlash.cpp
@@ -176,12 +176,12 @@ void SPIFlash::writeByte(long addr, uint8_t byt) {
 /// WARNING: if you write beyond a page boundary (or more than 256bytes),
 ///          the bytes will wrap around and start overwriting at the beginning of that same page
 ///          see datasheet for more details
-void SPIFlash::writeBytes(long addr, const void* buf, uint8_t len) {
+void SPIFlash::writeBytes(long addr, const void* buf, uint16_t len) {
   command(SPIFLASH_BYTEPAGEPROGRAM, true);  // Byte/Page Program
   SPI.transfer(addr >> 16);
   SPI.transfer(addr >> 8);
   SPI.transfer(addr);
-  for (uint8_t i = 0; i < len; i++)
+  for (uint16_t i = 0; i < len; i++)
     SPI.transfer(((byte*) buf)[i]);
   unselect();
 }
@@ -228,4 +228,4 @@ void SPIFlash::wakeup() {
 /// cleanup
 void SPIFlash::end() {
   SPI.end();
-}
+}
\ No newline at end of file
diff --git a/SPIFlash.h b/SPIFlash.h
index be049d4..20863c1 100644
--- a/SPIFlash.h
+++ b/SPIFlash.h
@@ -77,7 +77,7 @@ public:
   byte readByte(long addr);
   void readBytes(long addr, void* buf, word len);
   void writeByte(long addr, byte byt);
-  void writeBytes(long addr, const void* buf, byte len);
+  void writeBytes(long addr, const void* buf, uint16_t len);
   boolean busy();
   void chipErase();
   void blockErase4K(long address);