diff --git a/README.md b/README.md
index 2746d16..3692113 100755
--- a/README.md
+++ b/README.md
@@ -16,7 +16,10 @@ The EVT boards can be attached directly to the Raspberry Pi as a "hat".  When bu
 
 The only pins that are required are 5V, GND, CRESET, SPI_MOSI, SPI_MISO, SPI_CLK, and SPI_CS.
 
-You can improve performance by attaching SPI_IO2 and SPI_IO3 and running `fomu-flash` in quad/qpi mode by specifying `-t 4` or `-t q`.
+The Pi's hardware SPI interface must be enabled in the kernel- use
+`raspi-config` or add `dtparam=spi=on` to `/boot/config.txt` and reboot before
+using.  You can improve performance by attaching SPI_IO2 and SPI_IO3 and running
+`fomu-flash` in quad/qpi mode by specifying `-t 4` or `-t q`.
 
 You can get serial interaction by connecting the UART pins, but they are not necessary for flashing.
 
@@ -55,4 +58,4 @@ You can verify the SPI flash was programmed with the `-v` command:
 
 ## Checking SPI Flash was Written
 
-You can "peek" at 256 bytes of SPI with `-p [offset]`.  This can be used to quickly verify that something was written.
\ No newline at end of file
+You can "peek" at 256 bytes of SPI with `-p [offset]`.  This can be used to quickly verify that something was written.