diff --git a/libraries/AP_InertialSensor/AP_InertialSensor_MPU6000.cpp b/libraries/AP_InertialSensor/AP_InertialSensor_MPU6000.cpp
index 2c19412e00..24fc4c4d81 100644
--- a/libraries/AP_InertialSensor/AP_InertialSensor_MPU6000.cpp
+++ b/libraries/AP_InertialSensor/AP_InertialSensor_MPU6000.cpp
@@ -870,7 +870,6 @@ void AP_InertialSensor_MPU6000::dmp_set_sensor_fusion_accel_gain(uint8_t gain)
 // Load initial memory values into DMP memory banks
 void AP_InertialSensor_MPU6000::dmp_load_mem()
 {
-	uint8_t dump;
 
 	for(int i = 0; i < 7; i++) {
 		register_write(MPUREG_BANK_SEL,i);      //MPUREG_BANK_SEL
@@ -878,10 +877,10 @@ void AP_InertialSensor_MPU6000::dmp_load_mem()
 			uint8_t start_addy = j * 0x10;
 			register_write(MPUREG_MEM_START_ADDR,start_addy);
 			digitalWrite(_cs_pin, LOW);
-			dump = SPI.transfer(MPUREG_MEM_R_W);
+			SPI.transfer(MPUREG_MEM_R_W);
 			for(int k = 0; k < 16; k++){
-				unsigned char byteToSend = pgm_read_byte(&(dmpMem[i][j][k]));
-				dump = SPI.transfer((uint8_t) byteToSend);
+				uint8_t byteToSend = pgm_read_byte(&(dmpMem[i][j][k]));
+				SPI.transfer((uint8_t) byteToSend);
 			}
 			digitalWrite(_cs_pin, HIGH);
 		}
@@ -892,28 +891,27 @@ void AP_InertialSensor_MPU6000::dmp_load_mem()
 		uint8_t start_addy = j * 0x10;
 		register_write(MPUREG_MEM_START_ADDR,start_addy);
 		digitalWrite(_cs_pin, LOW);
-		dump = SPI.transfer(MPUREG_MEM_R_W);
+		SPI.transfer(MPUREG_MEM_R_W);
 		for(int k = 0; k < 16; k++){
-			unsigned char byteToSend = pgm_read_byte(&(dmpMem[7][j][k]));
-			dump = SPI.transfer((uint8_t) byteToSend);
+			uint8_t byteToSend = pgm_read_byte(&(dmpMem[7][j][k]));
+			SPI.transfer((uint8_t) byteToSend);
 		}
 		digitalWrite(_cs_pin, HIGH);
 	}
 
 	register_write(MPUREG_MEM_START_ADDR,0x80);
 	digitalWrite(_cs_pin, LOW);
-	dump = SPI.transfer(MPUREG_MEM_R_W);
+	SPI.transfer(MPUREG_MEM_R_W);
 	for(int k = 0; k < 9; k++){
-		unsigned char byteToSend = pgm_read_byte(&(dmpMem[7][8][k]));
-		dump = SPI.transfer((uint8_t) byteToSend);
+		uint8_t byteToSend = pgm_read_byte(&(dmpMem[7][8][k]));
+		SPI.transfer((uint8_t) byteToSend);
 	}
 	digitalWrite(_cs_pin, HIGH);
 }
 
 // ========= DMP MEMORY ================================
 
-//dmpMem from dmpDefaultMantis.c
-unsigned char dmpMem[8][16][16] PROGMEM = {
+const uint8_t dmpMem[8][16][16] PROGMEM = {
   {
     {
       0xFB, 0x00, 0x00, 0x3E, 0x00, 0x0B, 0x00, 0x36, 0x00, 0x01, 0x00, 0x02, 0x00, 0x03, 0x00, 0x00    }
diff --git a/libraries/AP_InertialSensor/AP_InertialSensor_MPU6000.h b/libraries/AP_InertialSensor/AP_InertialSensor_MPU6000.h
index a506b95a81..fc1f4d3e6d 100644
--- a/libraries/AP_InertialSensor/AP_InertialSensor_MPU6000.h
+++ b/libraries/AP_InertialSensor/AP_InertialSensor_MPU6000.h
@@ -12,8 +12,8 @@
 
 #define DMP_FIFO_BUFFER_SIZE 72        // DMP FIFO buffer size
 
-//dmpMem from dmpDefaultMantis.c
-extern unsigned char dmpMem[8][16][16] PROGMEM;
+// DMP memory
+extern const uint8_t dmpMem[8][16][16] PROGMEM;
 
 class AP_InertialSensor_MPU6000 : public AP_InertialSensor
 {