diff --git a/ssd1306.h b/ssd1306.h
--- a/ssd1306.h
+++ b/ssd1306.h
@@ -12,6 +12,8 @@
 #define   SSD_CS_Low()      HAL_GPIO_WritePin(SSD_CS, 0)
 #define   SSD_CS_High()     HAL_GPIO_WritePin(SSD_CS, 1)
 
+#include "spi.h"
+
 // EMZ FIXME this won't really work
 #define   SPI_SendByte(data)  HAL_SPI_Transmit(spi_get(), &data, 1, 100) 
 //#define SPI_SendByte(data)