diff --git a/openpcd/firmware/src/pcd/rc632.c b/openpcd/firmware/src/pcd/rc632.c
index 620d0a0..5d45955 100644
--- a/openpcd/firmware/src/pcd/rc632.c
+++ b/openpcd/firmware/src/pcd/rc632.c
@@ -50,7 +50,7 @@
 
 #define SPI_MAX_XFER_LEN	65
 
-static AT91PS_SPI pSPI = AT91C_BASE_SPI;
+static const AT91PS_SPI pSPI = AT91C_BASE_SPI;
 
 /* SPI irq handler */
 static void spi_irq(void)