diff --git a/src/lattice.cpp b/src/lattice.cpp
index 41e775b..18aeeca 100644
--- a/src/lattice.cpp
+++ b/src/lattice.cpp
@@ -901,7 +901,7 @@ bool Lattice::loadConfiguration()
 /* SPI implementation */
 /* ------------------ */
 
-int Lattice::spi_put(uint8_t cmd, uint8_t *tx, uint8_t *rx, uint16_t len)
+int Lattice::spi_put(uint8_t cmd, uint8_t *tx, uint8_t *rx, uint32_t len)
 {
 	int xfer_len = len + 1;
 	uint8_t jtx[xfer_len];
@@ -927,7 +927,7 @@ int Lattice::spi_put(uint8_t cmd, uint8_t *tx, uint8_t *rx, uint16_t len)
 	return 0;
 }
 
-int Lattice::spi_put(uint8_t *tx, uint8_t *rx, uint16_t len)
+int Lattice::spi_put(uint8_t *tx, uint8_t *rx, uint32_t len)
 {
 	int xfer_len = len;
 	uint8_t jtx[xfer_len];
diff --git a/src/lattice.hpp b/src/lattice.hpp
index 48d9bf4..b5ddc46 100644
--- a/src/lattice.hpp
+++ b/src/lattice.hpp
@@ -43,8 +43,8 @@ class Lattice: public Device, SPIInterface {
 
 		/* spi interface */
 		int spi_put(uint8_t cmd, uint8_t *tx, uint8_t *rx,
-		uint16_t len) override;
-		int spi_put(uint8_t *tx, uint8_t *rx, uint16_t len) override;
+		uint32_t len) override;
+		int spi_put(uint8_t *tx, uint8_t *rx, uint32_t len) override;
 		int spi_wait(uint8_t cmd, uint8_t mask, uint8_t cond,
 				uint32_t timeout, bool verbose=false) override;
 
diff --git a/src/spiInterface.hpp b/src/spiInterface.hpp
index 92cd1c1..f0190b1 100644
--- a/src/spiInterface.hpp
+++ b/src/spiInterface.hpp
@@ -42,7 +42,7 @@ class SPIInterface {
 	 * \return 0 when success
 	 */
 	virtual int spi_put(uint8_t cmd, uint8_t *tx, uint8_t *rx,
-						uint16_t len) = 0;
+						uint32_t len) = 0;
 
 	/*!
 	 * \brief send a command, followed by len byte.
@@ -51,7 +51,7 @@ class SPIInterface {
 	 * \param[in] len: number of byte to send/receive
 	 * \return 0 when success
 	 */
-	virtual int spi_put(uint8_t *tx, uint8_t *rx, uint16_t len) = 0;
+	virtual int spi_put(uint8_t *tx, uint8_t *rx, uint32_t len) = 0;
 
 	/*!
 	 * \brief wait until register content and mask match cond, or timeout
diff --git a/src/xilinx.cpp b/src/xilinx.cpp
index 640190f..eb1f1f6 100644
--- a/src/xilinx.cpp
+++ b/src/xilinx.cpp
@@ -217,7 +217,7 @@ void Xilinx::program_mem(BitParser &bitfile)
  *        so to send only a cmd set len to 0 (or omit this param)
  */
 int Xilinx::spi_put(uint8_t cmd,
-			uint8_t *tx, uint8_t *rx, uint16_t len)
+			uint8_t *tx, uint8_t *rx, uint32_t len)
 {
 	int xfer_len = len + 1 + ((rx == NULL) ? 0 : 1);
 	uint8_t jtx[xfer_len];
@@ -243,7 +243,7 @@ int Xilinx::spi_put(uint8_t cmd,
 	return 0;
 }
 
-int Xilinx::spi_put(uint8_t *tx, uint8_t *rx, uint16_t len)
+int Xilinx::spi_put(uint8_t *tx, uint8_t *rx, uint32_t len)
 {
 	int xfer_len = len + ((rx == NULL) ? 0 : 1);
 	uint8_t jtx[xfer_len];
diff --git a/src/xilinx.hpp b/src/xilinx.hpp
index a7b56fb..c00496c 100644
--- a/src/xilinx.hpp
+++ b/src/xilinx.hpp
@@ -21,8 +21,8 @@ class Xilinx: public Device, SPIInterface {
 
 		/* spi interface */
 		int spi_put(uint8_t cmd, uint8_t *tx, uint8_t *rx,
-				uint16_t len) override;
-		int spi_put(uint8_t *tx, uint8_t *rx, uint16_t len) override;
+				uint32_t len) override;
+		int spi_put(uint8_t *tx, uint8_t *rx, uint32_t len) override;
 		int spi_wait(uint8_t cmd, uint8_t mask, uint8_t cond,
 				uint32_t timeout, bool verbose = false) override;
 };