diff --git a/avrpins.h b/avrpins.h
index fd4fdf39..5eb679fb 100644
--- a/avrpins.h
+++ b/avrpins.h
@@ -613,7 +613,7 @@ public:
 // Arduino Leonardo pin numbers
 
 #elif defined(CORE_TEENSY) && (defined(__AVR_AT90USB646__) || defined(__AVR_AT90USB1286__))
-// Teensy++ 2.0 pin numbers
+// Teensy++ 1.0 and 2.0 pin numbers
 // http://www.pjrc.com/teensy/pinout.html
 #define P0  Pd0
 #define P1  Pd1
@@ -661,7 +661,7 @@ public:
 #define P43 Pf5
 #define P44 Pf6
 #define P45 Pf7
-// Teensy++ 2.0
+// Teensy++ 1.0 and 2.0
 
 #elif defined(ARDUINO_AVR_BALANDUINO) && (defined(__AVR_ATmega644__) || defined(__AVR_ATmega1284P__))
 // Balanduino pin numbers
@@ -738,6 +738,9 @@ public:
 #define P31 Pa7
 // Sanguino
 
+#else
+#error "Please define board in avrpins.h"
+
 #endif // Arduino pin definitions
 
 #endif // __AVR__
diff --git a/usbhost.h b/usbhost.h
index 04341923..26b8036f 100644
--- a/usbhost.h
+++ b/usbhost.h
@@ -44,15 +44,14 @@ public:
 /* SPI pin definitions. see avrpins.h   */
 #if defined(__AVR_ATmega1280__) || (__AVR_ATmega2560__) || defined(__AVR_ATmega32U4__) || defined(__AVR_AT90USB646__) || defined(__AVR_AT90USB1286__)
 typedef SPi< Pb1, Pb2, Pb3, Pb0 > spi;
-#endif
-#if  defined(__AVR_ATmega168__) || defined(__AVR_ATmega328P__)
+#elif  defined(__AVR_ATmega168__) || defined(__AVR_ATmega328P__)
 typedef SPi< Pb5, Pb3, Pb4, Pb2 > spi;
-#endif
-#if defined(__AVR_ATmega644__) || defined(__AVR_ATmega644P__) || defined(__AVR_ATmega1284__) || defined(__AVR_ATmega1284P__)
+#elif defined(__AVR_ATmega644__) || defined(__AVR_ATmega644P__) || defined(__AVR_ATmega1284__) || defined(__AVR_ATmega1284P__)
 typedef SPi< Pb7, Pb5, Pb6, Pb4 > spi;
-#endif
-#if defined(__MK20DX128__)
+#elif defined(__MK20DX128__)
 typedef SPi< P13, P11, P12, P10 > spi;
+#else
+#error "No SPI entry in usbhost.h"
 #endif
 
 typedef enum {