diff --git a/clock.c b/clock.c
index 53adf65..d0868c2 100644
--- a/clock.c
+++ b/clock.c
@@ -16,6 +16,7 @@
 #ifdef	TEMP_INTERCOM
 	#include	"intercom.h"
 #endif
+#include	"memory_barrier.h"
 
 /*!	do stuff every 1/4 second
 
@@ -25,8 +26,14 @@ void clock_250ms() {
 	if (steptimeout > (30 * 4)) {
 		power_off();
 	}
-	else if (heaters_all_off())
+	else if (heaters_all_off())	{
+		uint8_t save_reg = SREG;
+		cli();
+		CLI_SEI_BUG_MEMORY_BARRIER();
 		steptimeout++;
+		MEMORY_BARRIER();
+		SREG = save_reg;
+	}
 
 	ifclock(CLOCK_FLAG_1S) {
 		if (debug_flags & DEBUG_POSITION) {
diff --git a/dda.c b/dda.c
index 846af3a..ac62a54 100644
--- a/dda.c
+++ b/dda.c
@@ -23,7 +23,7 @@
 #endif
 
 /// step timeout
-uint8_t	steptimeout = 0;
+volatile uint8_t	steptimeout = 0;
 
 /*
 	position tracking
diff --git a/dda.h b/dda.h
index 4d05685..6699d27 100644
--- a/dda.h
+++ b/dda.h
@@ -122,7 +122,8 @@ typedef struct {
 */
 
 /// steptimeout is set to zero when we step, and increases over time so we can turn the motors off when they've been idle for a while
-extern uint8_t steptimeout;
+/// It is also used inside and outside of interrupts, which is why it has been made volatile
+extern volatile uint8_t steptimeout;
 
 /// startpoint holds the endpoint of the most recently created DDA, so we know where the next one created starts. could also be called last_endpoint
 extern TARGET startpoint;