diff --git a/include/spi.h b/include/spi.h
index 0b68c32..9ae98d6 100644
--- a/include/spi.h
+++ b/include/spi.h
@@ -1,3 +1,6 @@
+#ifndef __NRF52_SPI_H__
+#define __NRF52_SPI_H__
+
 int spi_open(const struct driver *drv);
 int spi_close(const struct driver *drv);
 
@@ -16,3 +19,5 @@ static const struct driver_fp spi_fp = {
     .write = spi_write,
     .ioctl = NULL
 };
+
+#endif
diff --git a/src/platform/nrf52/spi.c b/src/platform/nrf52/spi.c
index cbcea76..419e8d1 100644
--- a/src/platform/nrf52/spi.c
+++ b/src/platform/nrf52/spi.c
@@ -8,7 +8,6 @@
 
 static inline int spi_transfer(uint32_t t);
 
-
 int spi_open(const struct driver *drv)
 {
     assert(NULL != drv);
@@ -59,4 +58,3 @@ static inline int spi_transfer(uint32_t t)
     }
     r = NRF_SPI0->RXD;                    // in
     return (int)r;
-}