diff --git a/radio/src/targets/gruvin9x/board.h b/radio/src/targets/gruvin9x/board.h
index 6a5eceff0..597304f6b 100644
--- a/radio/src/targets/gruvin9x/board.h
+++ b/radio/src/targets/gruvin9x/board.h
@@ -73,6 +73,7 @@ void boardInit(void);
 #define JACK_PPM_IN()              PORTG &= ~(1<<OUT_G_SIM_CTL)
 
 // SD driver
+#define BLOCK_SIZE                     512 /* Block Size in Bytes */
 #define sdDone()
 #define SD_IS_HC()               (0)
 #define SD_GET_SPEED()           (0)
diff --git a/radio/src/targets/mega2560/board.h b/radio/src/targets/mega2560/board.h
index 940c7bfc2..68581c473 100644
--- a/radio/src/targets/mega2560/board.h
+++ b/radio/src/targets/mega2560/board.h
@@ -81,6 +81,7 @@ void boardInit(void);
 #define isBacklightEnable()       PORTC & (1<<OUT_C_LIGHT)
 
 // SD driver
+#define BLOCK_SIZE                     512 /* Block Size in Bytes */
 #define sdDone()
 #define SD_IS_HC()                (0)
 #define SD_GET_SPEED()            (0)