diff --git a/crc.c b/crc.c
index b3ecf8f..9a52512 100644
--- a/crc.c
+++ b/crc.c
@@ -4,7 +4,7 @@
 	\brief crc16 routine
 */
 
-#ifndef SIMULATOR
+#ifdef __AVR__
 #include	<util/crc16.h>
 #else
 
diff --git a/dda.c b/dda.c
index d1128b8..e9b3912 100644
--- a/dda.c
+++ b/dda.c
@@ -7,7 +7,7 @@
 #include	<string.h>
 #include	<stdlib.h>
 #include	<math.h>
-#ifndef SIMULATOR
+#ifdef __AVR__
 #include	<avr/interrupt.h>
 #endif
 
diff --git a/dda_lookahead.c b/dda_lookahead.c
index 60c856a..02f7597 100644
--- a/dda_lookahead.c
+++ b/dda_lookahead.c
@@ -11,7 +11,7 @@
 #include <stdlib.h>
 #include <stddef.h>
 #include <math.h>
-#ifndef SIMULATOR
+#ifdef __AVR__
 #include <avr/interrupt.h>
 #endif
 
diff --git a/dda_queue.c b/dda_queue.c
index 9b2e26d..ae184f5 100644
--- a/dda_queue.c
+++ b/dda_queue.c
@@ -5,7 +5,7 @@
 */
 
 #include	<string.h>
-#ifndef SIMULATOR
+#ifdef __AVR__
 #include	<avr/interrupt.h>
 #endif
 
diff --git a/gcode_process.c b/gcode_process.c
index 79c2435..cb9e23b 100644
--- a/gcode_process.c
+++ b/gcode_process.c
@@ -5,7 +5,7 @@
 */
 
 #include	<string.h>
-#ifndef SIMULATOR
+#ifdef __AVR__
 #include	<avr/interrupt.h>
 #endif
 
diff --git a/intercom.c b/intercom.c
index 25b83ac..6cca1df 100644
--- a/intercom.c
+++ b/intercom.c
@@ -4,7 +4,7 @@
 	\brief motherboard <-> extruder board protocol
 */
 
-#ifndef SIMULATOR
+#ifdef __AVR__
 #include	<avr/io.h>
 #include	<avr/interrupt.h>
 #endif
diff --git a/memory_barrier.h b/memory_barrier.h
index 2af71f7..6d3a3c7 100644
--- a/memory_barrier.h
+++ b/memory_barrier.h
@@ -13,7 +13,7 @@
                          if (save_reg) sei(); \
                        }
 
-#else
+#elif defined __AVR__
 #include <util/atomic.h>
 #include <avr/version.h>
 
diff --git a/temp.c b/temp.c
index 3cdcde7..fdeb32f 100644
--- a/temp.c
+++ b/temp.c
@@ -10,7 +10,7 @@
 */
 
 #include	<stdlib.h>
-#ifndef SIMULATOR
+#ifdef __AVR__
 #include	<avr/eeprom.h>
 #include	<avr/pgmspace.h>
 #endif
diff --git a/timer.c b/timer.c
index 6ed99cb..ce77f6f 100644
--- a/timer.c
+++ b/timer.c
@@ -10,7 +10,7 @@
 	Teacup has tried numerous timer management methods, and this is the best so far.
 */
 
-#ifndef SIMULATOR
+#ifdef __AVR__
 #include	<avr/interrupt.h>
 #endif
 #include	"memory_barrier.h"
diff --git a/timer.h b/timer.h
index a7118e1..1ba70ef 100644
--- a/timer.h
+++ b/timer.h
@@ -2,7 +2,7 @@
 #define	_TIMER_H
 
 #include	<stdint.h>
-#ifndef SIMULATOR
+#ifdef __AVR__
 #include	<avr/io.h>
 #endif
 #include "simulator.h"